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	"id": "751d7c08-58bb-43d3-92ae-c318f7904655",
	"created_at": "2026-04-06T00:16:40.395676Z",
	"updated_at": "2026-04-10T03:31:18.930802Z",
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	"sha1_hash": "adcbaeaf8de52a47c029d669853eeb8f3dd1a61a",
	"title": "bash(1): GNU Bourne-Again SHell - Linux man page",
	"llm_title": "",
	"authors": "",
	"file_creation_date": "0001-01-01T00:00:00Z",
	"file_modification_date": "0001-01-01T00:00:00Z",
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	"plain_text": "bash(1): GNU Bourne-Again SHell - Linux man page\r\nArchived: 2026-04-05 20:02:56 UTC\r\nName\r\nbash - GNU Bourne-Again SHell\r\nSynopsis\r\nbash [options] [file]\r\nCopyright\r\nBash is Copyright © 1989-2009 by the Free Software Foundation, Inc.\r\nDescription\r\nBash is an sh-compatible command language interpreter that executes commands read from the standard input or\r\nfrom a file. Bash also incorporates useful features from the Korn and C shells (ksh and csh).\r\nBash is intended to be a conformant implementation of the Shell and Utilities portion of the IEEE POSIX\r\nspecification (IEEE Standard 1003.1). Bash can be configured to be POSIX-conformant by default.\r\nOptions\r\nIn addition to the single-character shell options documented in the description of the set builtin command, bash\r\ninterprets the following options when it is invoked:\r\n-c string\r\nIf the -c option is present, then commands are read from string. If there are arguments after the string, they are\r\nassigned to the positional parameters, starting with $0.\r\n-i\r\nIf the -i option is present, the shell is interactive.\r\n-l\r\nMake bash act as if it had been invoked as a login shell (see INVOCATION below).\r\n-r\r\nIf the -r option is present, the shell becomes restricted (see RESTRICTED SHELL below).\r\nhttps://linux.die.net/man/1/bash\r\nPage 1 of 107\n\n-s\r\nIf the -s option is present, or if no arguments remain after option processing, then commands are read from the\r\nstandard input. This option allows the positional parameters to be set when invoking an interactive shell.\r\n-D\r\nA list of all double-quoted strings preceded by $ is printed on the standard output. These are the strings that are\r\nsubject to language translation when the current locale is not C or POSIX. This implies the -n option; no\r\ncommands will be executed.\r\n[-+]O [shopt_option]\r\nshopt_option is one of the shell options accepted by the shopt builtin (see SHELL BUILTIN COMMANDS\r\nbelow). If shopt_option is present, -O sets the value of that option; +O unsets it. If shopt_option is not\r\nsupplied, the names and values of the shell options accepted by shopt are printed on the standard output. If\r\nthe invocation option is +O, the output is displayed in a format that may be reused as input.\r\n--\r\nA -- signals the end of options and disables further option processing. Any arguments after the -- are treated as\r\nfilenames and arguments. An argument of - is equivalent to --.\r\nBash also interprets a number of multi-character options. These options must appear on the command line before\r\nthe single-character options to be recognized.\r\n--debugger\r\nArrange for the debugger profile to be executed before the shell starts. Turns on extended debugging mode\r\n(see the description of the extdebug option to the shopt builtin below) and shell function tracing (see the\r\ndescription of the -o functrace option to the set builtin below).\r\n--dump-po-strings\r\nEquivalent to -D, but the output is in the GNU gettext po (portable object) file format.\r\n--dump-strings\r\nEquivalent to -D.\r\n--help\r\nDisplay a usage message on standard output and exit successfully.\r\n--init-file file\r\n--rcfile file\r\nExecute commands from file instead of the standard personal initialization file ~/.bashrc if the shell is\r\ninteractive (see INVOCATION below).\r\n--login\r\nEquivalent to -l.\r\n--noediting\r\nDo not use the GNU readline library to read command lines when the shell is interactive.\r\n--noprofile\r\nhttps://linux.die.net/man/1/bash\r\nPage 2 of 107\n\nDo not read either the system-wide startup file /etc/profile or any of the personal initialization files\r\n~/.bash_profile, ~/.bash_login, or ~/.profile. By default, bash reads these files when it is invoked as a login\r\nshell (see INVOCATION below).\r\n--norc\r\nDo not read and execute the personal initialization file ~/.bashrc if the shell is interactive. This option is on by\r\ndefault if the shell is invoked as sh.\r\n--posix\r\nChange the behavior of bash where the default operation differs from the POSIX standard to match the\r\nstandard (posix mode).\r\n--restricted\r\nThe shell becomes restricted (see RESTRICTED SHELL below).\r\n--rpm-requires\r\nProduce the list of files that are required for the shell script to run. This implies '-n' and is subject to the\r\nsame limitations as compile time error checking checking; Backticks, [] tests, and evals are not parsed so\r\nsome dependencies may be missed.\r\n--verbose\r\nEquivalent to -v.\r\n--version\r\nShow version information for this instance of bash on the standard output and exit successfully.\r\nArguments\r\nIf arguments remain after option processing, and neither the -c nor the -s option has been supplied, the first\r\nargument is assumed to be the name of a file containing shell commands. If bash is invoked in this fashion, $0 is\r\nset to the name of the file, and the positional parameters are set to the remaining arguments. Bash reads and\r\nexecutes commands from this file, then exits. Bash's exit status is the exit status of the last command executed in\r\nthe script. If no commands are executed, the exit status is 0. An attempt is first made to open the file in the current\r\ndirectory, and, if no file is found, then the shell searches the directories in PATH for the script.\r\nInvocation\r\nA login shell is one whose first character of argument zero is a -, or one started with the --login option.\r\nAn interactive shell is one started without non-option arguments and without the -c option whose standard input\r\nand error are both connected to terminals (as determined by isatty(3)), or one started with the -i option. PS1 is set\r\nand $- includes i if bash is interactive, allowing a shell script or a startup file to test this state.\r\nThe following paragraphs describe how bash executes its startup files. If any of the files exist but cannot be read,\r\nbash reports an error. Tildes are expanded in file names as described below under Tilde Expansion in the\r\nEXPANSION section.\r\nWhen bash is invoked as an interactive login shell, or as a non-interactive shell with the --login option, it first\r\nreads and executes commands from the file /etc/profile, if that file exists. After reading that file, it looks for\r\nhttps://linux.die.net/man/1/bash\r\nPage 3 of 107\n\n~/.bash_profile, ~/.bash_login, and ~/.profile, in that order, and reads and executes commands from the first one\r\nthat exists and is readable. The --noprofile option may be used when the shell is started to inhibit this behavior.\r\nWhen a login shell exits, bash reads and executes commands from the files ~/.bash_logout and\r\n/etc/bash.bash_logout, if the files exists.\r\nWhen an interactive shell that is not a login shell is started, bash reads and executes commands from ~/.bashrc, if\r\nthat file exists. This may be inhibited by using the --norc option. The --rcfile file option will force bash to read\r\nand execute commands from file instead of ~/.bashrc.\r\nWhen bash is started non-interactively, to run a shell script, for example, it looks for the variable BASH_ENV in\r\nthe environment, expands its value if it appears there, and uses the expanded value as the name of a file to read\r\nand execute. Bash behaves as if the following command were executed:\r\nif [ -n \"$BASH_ENV\" ]; then . \"$BASH_ENV\"; fi\r\nbut the value of the PATH variable is not used to search for the file name.\r\nIf bash is invoked with the name sh, it tries to mimic the startup behavior of historical versions of sh as closely as\r\npossible, while conforming to the POSIX standard as well. When invoked as an interactive login shell, or a non-interactive shell with the --login option, it first attempts to read and execute commands from /etc/profile and\r\n~/.profile, in that order. The --noprofile option may be used to inhibit this behavior. When invoked as an\r\ninteractive shell with the name sh, bash looks for the variable ENV, expands its value if it is defined, and uses the\r\nexpanded value as the name of a file to read and execute. Since a shell invoked as sh does not attempt to read and\r\nexecute commands from any other startup files, the --rcfile option has no effect. A non-interactive shell invoked\r\nwith the name sh does not attempt to read any other startup files. When invoked as sh, bash enters posix mode\r\nafter the startup files are read.\r\nWhen bash is started in posix mode, as with the --posix command line option, it follows the POSIX standard for\r\nstartup files. In this mode, interactive shells expand the ENV variable and commands are read and executed from\r\nthe file whose name is the expanded value. No other startup files are read.\r\nBash attempts to determine when it is being run with its standard input connected to a a network connection, as if\r\nby the remote shell daemon, usually rshd, or the secure shell daemon sshd. If bash determines it is being run in\r\nthis fashion, it reads and executes commands from ~/.bashrc, if that file exists and is readable. It will not do this if\r\ninvoked as sh. The --norc option may be used to inhibit this behavior, and the --rcfile option may be used to force\r\nanother file to be read, but rshd does not generally invoke the shell with those options or allow them to be\r\nspecified.\r\nIf the shell is started with the effective user (group) id not equal to the real user (group) id, and the -p option is not\r\nsupplied, no startup files are read, shell functions are not inherited from the environment, the SHELLOPTS,\r\nBASHOPTS, CDPATH, and GLOBIGNORE variables, if they appear in the environment, are ignored, and the\r\neffective user id is set to the real user id. If the -p option is supplied at invocation, the startup behavior is the same,\r\nbut the effective user id is not reset.\r\nDefinitions\r\nhttps://linux.die.net/man/1/bash\r\nPage 4 of 107\n\nThe following definitions are used throughout the rest of this document.\r\nblank\r\nA space or tab.\r\nword\r\nA sequence of characters considered as a single unit by the shell. Also known as a token.\r\nname\r\nA word consisting only of alphanumeric characters and underscores, and beginning with an alphabetic character or\r\nan underscore. Also referred to as an identifier.\r\nmetacharacter\r\nA character that, when unquoted, separates words. One of the following:\r\n| \u0026 ; ( ) \u003c \u003e space tab\r\ncontrol operator\r\nA token that performs a control function. It is one of the following symbols:\r\n|| \u0026 \u0026\u0026 ; ;; ( ) | |\u0026 \u003cnewline\u003e\r\nReserved Words\r\nReserved words are words that have a special meaning to the shell. The following words are recognized as\r\nreserved when unquoted and either the first word of a simple command (see SHELL GRAMMAR below) or the third\r\nword of a case or for command:\r\n! case do done elif else esac fi for function if in select then until while { } time [[ ]]\r\nShell Grammar\r\nSimple Commands\r\nA simple command is a sequence of optional variable assignments followed by blank-separated words and\r\nredirections, and terminated by a control operator. The first word specifies the command to be executed, and is\r\npassed as argument zero. The remaining words are passed as arguments to the invoked command.\r\nThe return value of a simple command is its exit status, or 128+n if the command is terminated by signal n.\r\nPipelines\r\nA pipeline is a sequence of one or more commands separated by one of the control operators | or |\u0026. The format\r\nfor a pipeline is:\r\n[time [-p]] [ ! ] command [ [|│|\u0026] command2 ... ]\r\nThe standard output of command is connected via a pipe to the standard input of command2. This connection is\r\nperformed before any redirections specified by the command (see REDIRECTION below). If |\u0026 is used, the\r\nhttps://linux.die.net/man/1/bash\r\nPage 5 of 107\n\nstandard error of command is connected to command2's standard input through the pipe; it is shorthand for 2\u003e\u00261\r\n|. This implicit redirection of the standard error is performed after any redirections specified by the command.\r\nThe return status of a pipeline is the exit status of the last command, unless the pipefail option is enabled. If\r\npipefail is enabled, the pipeline's return status is the value of the last (rightmost) command to exit with a non-zero\r\nstatus, or zero if all commands exit successfully. If the reserved word ! precedes a pipeline, the exit status of that\r\npipeline is the logical negation of the exit status as described above. The shell waits for all commands in the\r\npipeline to terminate before returning a value.\r\nIf the time reserved word precedes a pipeline, the elapsed as well as user and system time consumed by its\r\nexecution are reported when the pipeline terminates. The -p option changes the output format to that specified by\r\nPOSIX. The TIMEFORMAT variable may be set to a format string that specifies how the timing information should\r\nbe displayed; see the description of TIMEFORMAT under Shell Variables below.\r\nEach command in a pipeline is executed as a separate process (i.e., in a subshell).\r\nLists\r\nA list is a sequence of one or more pipelines separated by one of the operators ;, \u0026, \u0026\u0026, or ││, and optionally\r\nterminated by one of ;, \u0026, or \u003cnewline\u003e.\r\nOf these list operators, \u0026\u0026 and ││ have equal precedence, followed by ; and \u0026, which have equal precedence.\r\nA sequence of one or more newlines may appear in a list instead of a semicolon to delimit commands.\r\nIf a command is terminated by the control operator \u0026, the shell executes the command in the background in a\r\nsubshell. The shell does not wait for the command to finish, and the return status is 0. Commands separated by a ;\r\nare executed sequentially; the shell waits for each command to terminate in turn. The return status is the exit status\r\nof the last command executed.\r\nAND and OR lists are sequences of one of more pipelines separated by the \u0026\u0026 and ││ control operators,\r\nrespectively. AND and OR lists are executed with left associativity. An AND list has the form\r\ncommand1 \u0026\u0026 command2\r\ncommand2 is executed if, and only if, command1 returns an exit status of zero.\r\nAn OR list has the form\r\ncommand1 ││ command2\r\ncommand2 is executed if and only if command1 returns a non-zero exit status. The return status of AND and OR\r\nlists is the exit status of the last command executed in the list.\r\nCompound Commands\r\nA compound command is one of the following:\r\n(list)\r\nhttps://linux.die.net/man/1/bash\r\nPage 6 of 107\n\nlist is executed in a subshell environment (see COMMAND EXECUTION ENVIRONMENT below). Variable\r\nassignments and builtin commands that affect the shell's environment do not remain in effect after the command\r\ncompletes. The return status is the exit status of list.\r\n{ list; }\r\nlist is simply executed in the current shell environment. list must be terminated with a newline or\r\nsemicolon. This is known as a group command. The return status is the exit status of list. Note that unlike\r\nthe metacharacters ( and ), { and } are reserved words and must occur where a reserved word is permitted to\r\nbe recognized. Since they do not cause a word break, they must be separated from list by whitespace or\r\nanother shell metacharacter.\r\n((expression))\r\nThe expression is evaluated according to the rules described below under ARITHMETIC EVALUATION. If\r\nthe value of the expression is non-zero, the return status is 0; otherwise the return status is 1. This is exactly\r\nequivalent to let \"expression\".\r\n[[ expression ]]\r\nReturn a status of 0 or 1 depending on the evaluation of the conditional expression expression. Expressions\r\nare composed of the primaries described below under CONDITIONAL EXPRESSIONS. Word splitting and\r\npathname expansion are not performed on the words between the [[ and ]]; tilde expansion, parameter and\r\nvariable expansion, arithmetic expansion, command substitution, process substitution, and quote removal\r\nare performed. Conditional operators such as -f must be unquoted to be recognized as primaries.\r\nWhen used with [[, The \u003c and \u003e operators sort lexicographically using the current locale.\r\nWhen the == and != operators are used, the string to the right of the operator is considered a pattern and\r\nmatched according to the rules described below under Pattern Matching. If the shell option nocasematch\r\nis enabled, the match is performed without regard to the case of alphabetic characters. The return value is 0\r\nif the string matches (==) or does not match (!=) the pattern, and 1 otherwise. Any part of the pattern may\r\nbe quoted to force it to be matched as a string.\r\nAn additional binary operator, =~, is available, with the same precedence as == and !=. When it is used, the\r\nstring to the right of the operator is considered an extended regular expression and matched accordingly (as\r\nin regex(3)). The return value is 0 if the string matches the pattern, and 1 otherwise. If the regular\r\nexpression is syntactically incorrect, the conditional expression's return value is 2. If the shell option\r\nnocasematch is enabled, the match is performed without regard to the case of alphabetic characters. Any\r\npart of the pattern may be quoted to force it to be matched as a string. Substrings matched by parenthesized\r\nsubexpressions within the regular expression are saved in the array variable BASH_REMATCH. The element\r\nof BASH_REMATCH with index 0 is the portion of the string matching the entire regular expression. The\r\nelement of BASH_REMATCH with index n is the portion of the string matching the nth parenthesized\r\nsubexpression.\r\nExpressions may be combined using the following operators, listed in decreasing order of precedence:\r\n( expression )\r\nReturns the value of expression. This may be used to override the normal precedence of operators.\r\nhttps://linux.die.net/man/1/bash\r\nPage 7 of 107\n\n! expression\r\nTrue if expression is false.\r\nexpression1 \u0026\u0026 expression2\r\nTrue if both expression1 and expression2 are true.\r\nexpression1 || expression2\r\nTrue if either expression1 or expression2 is true.\r\nThe \u0026\u0026 and || operators do not evaluate expression2 if the value of expression1 is sufficient to determine\r\nthe return value of the entire conditional expression.\r\nfor name [ [ in [ word ... ] ] ; ] do list ; done\r\nThe list of words following in is expanded, generating a list of items. The variable name is set to each\r\nelement of this list in turn, and list is executed each time. If the in word is omitted, the for command\r\nexecutes list once for each positional parameter that is set (see PARAMETERS below). The return status is\r\nthe exit status of the last command that executes. If the expansion of the items following in results in an\r\nempty list, no commands are executed, and the return status is 0.\r\nfor (( expr1 ; expr2 ; expr3 )) ; do list ; done\r\nFirst, the arithmetic expression expr1 is evaluated according to the rules described below under\r\nARITHMETIC EVALUATION. The arithmetic expression expr2 is then evaluated repeatedly until it evaluates\r\nto zero. Each time expr2 evaluates to a non-zero value, list is executed and the arithmetic expression expr3\r\nis evaluated. If any expression is omitted, it behaves as if it evaluates to 1. The return value is the exit\r\nstatus of the last command in list that is executed, or false if any of the expressions is invalid.\r\nselect name [ in word ] ; do list ; done\r\nThe list of words following in is expanded, generating a list of items. The set of expanded words is printed\r\non the standard error, each preceded by a number. If the in word is omitted, the positional parameters are\r\nprinted (see PARAMETERS below). The PS3 prompt is then displayed and a line read from the standard\r\ninput. If the line consists of a number corresponding to one of the displayed words, then the value of name\r\nis set to that word. If the line is empty, the words and prompt are displayed again. If EOF is read, the\r\ncommand completes. Any other value read causes name to be set to null. The line read is saved in the\r\nvariable REPLY. The list is executed after each selection until a break command is executed. The exit\r\nstatus of select is the exit status of the last command executed in list, or zero if no commands were\r\nexecuted.\r\ncase word in [ [(] pattern [ | pattern ] ... ) list ;; ] ... esac\r\nA case command first expands word, and tries to match it against each pattern in turn, using the same\r\nmatching rules as for pathname expansion (see Pathname Expansion below). The word is expanded using\r\ntilde expansion, parameter and variable expansion, arithmetic substitution, command substitution, process\r\nsubstitution and quote removal. Each pattern examined is expanded using tilde expansion, parameter and\r\nvariable expansion, arithmetic substitution, command substitution, and process substitution. If the shell\r\noption nocasematch is enabled, the match is performed without regard to the case of alphabetic characters.\r\nWhen a match is found, the corresponding list is executed. If the ;; operator is used, no subsequent matches\r\nhttps://linux.die.net/man/1/bash\r\nPage 8 of 107\n\nare attempted after the first pattern match. Using ;\u0026 in place of ;; causes execution to continue with the list\r\nassociated with the next set of patterns. Using ;;\u0026 in place of ;; causes the shell to test the next pattern list\r\nin the statement, if any, and execute any associated list on a successful match. The exit status is zero if no\r\npattern matches. Otherwise, it is the exit status of the last command executed in list.\r\nif list; then list; [ elif list; then list; ] ... [ else list; ] fi\r\nThe if list is executed. If its exit status is zero, the then list is executed. Otherwise, each elif list is executed\r\nin turn, and if its exit status is zero, the corresponding then list is executed and the command completes.\r\nOtherwise, the else list is executed, if present. The exit status is the exit status of the last command\r\nexecuted, or zero if no condition tested true.\r\nwhile list; do list; done\r\nuntil list; do list; done\r\nThe while command continuously executes the do list as long as the last command in list returns an exit\r\nstatus of zero. The until command is identical to the while command, except that the test is negated; the do\r\nlist is executed as long as the last command in list returns a non-zero exit status. The exit status of the\r\nwhile and until commands is the exit status of the last do list command executed, or zero if none was\r\nexecuted.\r\nCoprocesses\r\nA coprocess is a shell command preceded by the coproc reserved word. A coprocess is executed asynchronously\r\nin a subshell, as if the command had been terminated with the \u0026 control operator, with a two-way pipe established\r\nbetween the executing shell and the coprocess.\r\nThe format for a coprocess is:\r\ncoproc [NAME] command [redirections]\r\nThis creates a coprocess named NAME. If NAME is not supplied, the default name is COPROC. NAME must not\r\nbe supplied if command is a simple command (see above); otherwise, it is interpreted as the first word of the\r\nsimple command. When the coproc is executed, the shell creates an array variable (see Arrays below) named\r\nNAME in the context of the executing shell. The standard output of command is connected via a pipe to a file\r\ndescriptor in the executing shell, and that file descriptor is assigned to NAME[0]. The standard input of command\r\nis connected via a pipe to a file descriptor in the executing shell, and that file descriptor is assigned to NAME[1].\r\nThis pipe is established before any redirections specified by the command (see REDIRECTION below). The file\r\ndescriptors can be utilized as arguments to shell commands and redirections using standard word expansions. The\r\nprocess id of the shell spawned to execute the coprocess is available as the value of the variable NAME_PID. The\r\nwait builtin command may be used to wait for the coprocess to terminate.\r\nThe return status of a coprocess is the exit status of command.\r\nShell Function Definitions\r\nA shell function is an object that is called like a simple command and executes a compound command with a new\r\nset of positional parameters. Shell functions are declared as follows:\r\n[ function ] name () compound-command [redirection]\r\nhttps://linux.die.net/man/1/bash\r\nPage 9 of 107\n\nThis defines a function named name. The reserved word function is optional. If the function reserved\r\nword is supplied, the parentheses are optional. The body of the function is the compound command\r\ncompound-command (see Compound Commands above). That command is usually a list of commands\r\nbetween { and }, but may be any command listed under Compound Commands above. compound-command is executed whenever name is specified as the name of a simple command. Any redirections (see\r\nREDIRECTION below) specified when a function is defined are performed when the function is executed.\r\nThe exit status of a function definition is zero unless a syntax error occurs or a readonly function with the\r\nsame name already exists. When executed, the exit status of a function is the exit status of the last\r\ncommand executed in the body. (See FUNCTIONS below.)\r\nComments\r\nIn a non-interactive shell, or an interactive shell in which the interactive_comments option to the shopt builtin is\r\nenabled (see SHELL BUILTIN COMMANDS below), a word beginning with # causes that word and all remaining\r\ncharacters on that line to be ignored. An interactive shell without the interactive_comments option enabled does\r\nnot allow comments. The interactive_comments option is on by default in interactive shells.\r\nQuoting\r\nQuoting is used to remove the special meaning of certain characters or words to the shell. Quoting can be used to\r\ndisable special treatment for special characters, to prevent reserved words from being recognized as such, and to\r\nprevent parameter expansion.\r\nEach of the metacharacters listed above under DEFINITIONS has special meaning to the shell and must be quoted\r\nif it is to represent itself.\r\nWhen the command history expansion facilities are being used (see HISTORY EXPANSION below), the history\r\nexpansion character, usually !, must be quoted to prevent history expansion.\r\nThere are three quoting mechanisms: the escape character, single quotes, and double quotes.\r\nA non-quoted backslash (\\) is the escape character. It preserves the literal value of the next character that follows,\r\nwith the exception of \u003cnewline\u003e. If a \\\u003cnewline\u003e pair appears, and the backslash is not itself quoted, the \\\r\n\u003cnewline\u003e is treated as a line continuation (that is, it is removed from the input stream and effectively ignored).\r\nEnclosing characters in single quotes preserves the literal value of each character within the quotes. A single quote\r\nmay not occur between single quotes, even when preceded by a backslash.\r\nEnclosing characters in double quotes preserves the literal value of all characters within the quotes, with the\r\nexception of $, `, \\, and, when history expansion is enabled, !. The characters $ and ` retain their special meaning\r\nwithin double quotes. The backslash retains its special meaning only when followed by one of the following\r\ncharacters: $, `, \", \\, or \u003cnewline\u003e. A double quote may be quoted within double quotes by preceding it with a\r\nbackslash. If enabled, history expansion will be performed unless an ! appearing in double quotes is escaped using\r\na backslash. The backslash preceding the ! is not removed.\r\nThe special parameters * and @ have special meaning when in double quotes (see PARAMETERS below).\r\nhttps://linux.die.net/man/1/bash\r\nPage 10 of 107\n\nWords of the form $'string' are treated specially. The word expands to string, with backslash-escaped characters\r\nreplaced as specified by the ANSI C standard. Backslash escape sequences, if present, are decoded as follows:\r\n\\a\r\nalert (bell)\r\n\\b\r\nbackspace\r\n\\e\r\n\\E\r\nan escape character\r\n\\f\r\nform feed\r\n\\n\r\nnew line\r\n\\r\r\ncarriage return\r\n\\t\r\nhorizontal tab\r\n\\v\r\nvertical tab\r\n\\\\\r\nbackslash\r\n\\'\r\nsingle quote\r\n\\\"\r\ndouble quote\r\n\\nnn\r\nthe eight-bit character whose value is the octal value nnn (one to three digits)\r\nhttps://linux.die.net/man/1/bash\r\nPage 11 of 107\n\n\\xHH\r\nthe eight-bit character whose value is the hexadecimal value HH (one or two hex digits)\r\n\\cx\r\na control-x character\r\nThe expanded result is single-quoted, as if the dollar sign had not been present.\r\nA double-quoted string preceded by a dollar sign ($\"string\") will cause the string to be translated according to the\r\ncurrent locale. If the current locale is C or POSIX, the dollar sign is ignored. If the string is translated and\r\nreplaced, the replacement is double-quoted.\r\nParameters\r\nA parameter is an entity that stores values. It can be a name, a number, or one of the special characters listed\r\nbelow under Special Parameters. A variable is a parameter denoted by a name. A variable has a value and zero or\r\nmore attributes. Attributes are assigned using the declare builtin command (see declare below in SHELL BUILTIN\r\nCOMMANDS).\r\nA parameter is set if it has been assigned a value. The null string is a valid value. Once a variable is set, it may be\r\nunset only by using the unset builtin command (see SHELL BUILTIN COMMANDS below).\r\nA variable may be assigned to by a statement of the form\r\nname=[value]\r\nIf value is not given, the variable is assigned the null string. All values undergo tilde expansion, parameter and\r\nvariable expansion, command substitution, arithmetic expansion, and quote removal (see EXPANSION below). If\r\nthe variable has its integer attribute set, then value is evaluated as an arithmetic expression even if the $((...))\r\nexpansion is not used (see Arithmetic Expansion below). Word splitting is not performed, with the exception of\r\n\"$@\" as explained below under Special Parameters. Pathname expansion is not performed. Assignment\r\nstatements may also appear as arguments to the alias, declare, typeset, export, readonly, and local builtin\r\ncommands.\r\nIn the context where an assignment statement is assigning a value to a shell variable or array index, the +=\r\noperator can be used to append to or add to the variable's previous value. When += is applied to a variable for\r\nwhich the integer attribute has been set, value is evaluated as an arithmetic expression and added to the variable's\r\ncurrent value, which is also evaluated. When += is applied to an array variable using compound assignment (see\r\nArrays below), the variable's value is not unset (as it is when using =), and new values are appended to the array\r\nbeginning at one greater than the array's maximum index (for indexed arrays) or added as additional key-value\r\npairs in an associative array. When applied to a string-valued variable, value is expanded and appended to the\r\nvariable's value.\r\nPositional Parameters\r\nhttps://linux.die.net/man/1/bash\r\nPage 12 of 107\n\nA positional parameter is a parameter denoted by one or more digits, other than the single digit 0. Positional\r\nparameters are assigned from the shell's arguments when it is invoked, and may be reassigned using the set builtin\r\ncommand. Positional parameters may not be assigned to with assignment statements. The positional parameters\r\nare temporarily replaced when a shell function is executed (see FUNCTIONS below).\r\nWhen a positional parameter consisting of more than a single digit is expanded, it must be enclosed in braces (see\r\nEXPANSION below).\r\nSpecial Parameters\r\nThe shell treats several parameters specially. These parameters may only be referenced; assignment to them is not\r\nallowed.\r\n*\r\nExpands to the positional parameters, starting from one. When the expansion occurs within double quotes, it\r\nexpands to a single word with the value of each parameter separated by the first character of the IFS special\r\nvariable. That is, \"$*\" is equivalent to \"$1c$2c...\", where c is the first character of the value of the IFS variable. If\r\nIFS is unset, the parameters are separated by spaces. If IFS is null, the parameters are joined without intervening\r\nseparators.\r\n@\r\nExpands to the positional parameters, starting from one. When the expansion occurs within double quotes, each\r\nparameter expands to a separate word. That is, \"$@\" is equivalent to \"$1\" \"$2\" ... If the double-quoted expansion\r\noccurs within a word, the expansion of the first parameter is joined with the beginning part of the original word,\r\nand the expansion of the last parameter is joined with the last part of the original word. When there are no\r\npositional parameters, \"$@\" and $@ expand to nothing (i.e., they are removed).\r\n#\r\nExpands to the number of positional parameters in decimal.\r\n?\r\nExpands to the exit status of the most recently executed foreground pipeline.\r\n-\r\nExpands to the current option flags as specified upon invocation, by the set builtin command, or those set by the\r\nshell itself (such as the -i option).\r\n$\r\nExpands to the process ID of the shell. In a () subshell, it expands to the process ID of the current shell, not the\r\nsubshell.\r\n!\r\nhttps://linux.die.net/man/1/bash\r\nPage 13 of 107\n\nExpands to the process ID of the most recently executed background (asynchronous) command.\r\n0\r\nExpands to the name of the shell or shell script. This is set at shell initialization. If bash is invoked with a file of\r\ncommands, $0 is set to the name of that file. If bash is started with the -c option, then $0 is set to the first\r\nargument after the string to be executed, if one is present. Otherwise, it is set to the file name used to invoke bash,\r\nas given by argument zero.\r\n_\r\nAt shell startup, set to the absolute pathname used to invoke the shell or shell script being executed as passed in\r\nthe environment or argument list. Subsequently, expands to the last argument to the previous command, after\r\nexpansion. Also set to the full pathname used to invoke each command executed and placed in the environment\r\nexported to that command. When checking mail, this parameter holds the name of the mail file currently being\r\nchecked.\r\nShell Variables\r\nThe following variables are set by the shell:\r\nBASH\r\nExpands to the full file name used to invoke this instance of bash.\r\nBASHOPTS\r\nA colon-separated list of enabled shell options. Each word in the list is a valid argument for the -s option to\r\nthe shopt builtin command (see SHELL BUILTIN COMMANDS below). The options appearing in BASHOPTS\r\nare those reported as on by shopt. If this variable is in the environment when bash starts up, each shell\r\noption in the list will be enabled before reading any startup files. This variable is read-only.\r\nBASHPID\r\nExpands to the process id of the current bash process. This differs from $$ under certain circumstances,\r\nsuch as subshells that do not require bash to be re-initialized.\r\nBASH_ALIASES\r\nAn associative array variable whose members correspond to the internal list of aliases as maintained by the\r\nalias builtin Elements added to this array appear in the alias list; unsetting array elements cause aliases to\r\nbe removed from the alias list.\r\nBASH_ARGC\r\nAn array variable whose values are the number of parameters in each frame of the current bash execution\r\ncall stack. The number of parameters to the current subroutine (shell function or script executed with . or\r\nsource) is at the top of the stack. When a subroutine is executed, the number of parameters passed is\r\npushed onto BASH_ARGC. The shell sets BASH_ARGC only when in extended debugging mode (see the\r\ndescription of the extdebug option to the shopt builtin below)\r\nBASH_ARGV\r\nAn array variable containing all of the parameters in the current bash execution call stack. The final\r\nparameter of the last subroutine call is at the top of the stack; the first parameter of the initial call is at the\r\nhttps://linux.die.net/man/1/bash\r\nPage 14 of 107\n\nbottom. When a subroutine is executed, the parameters supplied are pushed onto BASH_ARGV. The shell\r\nsets BASH_ARGV only when in extended debugging mode (see the description of the extdebug option to\r\nthe shopt builtin below)\r\nBASH_CMDS\r\nAn associative array variable whose members correspond to the internal hash table of commands as\r\nmaintained by the hash builtin. Elements added to this array appear in the hash table; unsetting array\r\nelements cause commands to be removed from the hash table.\r\nBASH_COMMAND\r\nThe command currently being executed or about to be executed, unless the shell is executing a command\r\nas the result of a trap, in which case it is the command executing at the time of the trap.\r\nBASH_EXECUTION_STRING\r\nThe command argument to the -c invocation option.\r\nBASH_LINENO\r\nAn array variable whose members are the line numbers in source files corresponding to each member of\r\nFUNCNAME. ${BASH_LINENO[$i]} is the line number in the source file where ${FUNCNAME[$i]} was\r\ncalled (or ${BASH_LINENO[$i-1]} if referenced within another shell function). The corresponding\r\nsource file name is ${BASH_SOURCE[$i]}. Use LINENO to obtain the current line number.\r\nBASH_REMATCH\r\nAn array variable whose members are assigned by the =~ binary operator to the [[ conditional command.\r\nThe element with index 0 is the portion of the string matching the entire regular expression. The element\r\nwith index n is the portion of the string matching the nth parenthesized subexpression. This variable is\r\nread-only.\r\nBASH_SOURCE\r\nAn array variable whose members are the source filenames corresponding to the elements in the\r\nFUNCNAME array variable.\r\nBASH_SUBSHELL\r\nIncremented by one each time a subshell or subshell environment is spawned. The initial value is 0.\r\nBASH_VERSINFO\r\nA readonly array variable whose members hold version information for this instance of bash. The values\r\nassigned to the array members are as follows:\r\nBASH_VERSINFO[0]\r\nThe major version number (the release).\r\nBASH_VERSINFO[1]\r\nThe minor version number (the version).\r\nBASH_VERSINFO[2]\r\nThe patch level.\r\nBASH_VERSINFO[3]\r\nThe build version.\r\nhttps://linux.die.net/man/1/bash\r\nPage 15 of 107\n\nBASH_VERSINFO[4]\r\nThe release status (e.g., beta1).\r\nBASH_VERSINFO[5]\r\nThe value of MACHTYPE.\r\nBASH_VERSION\r\nExpands to a string describing the version of this instance of bash.\r\nCOMP_CWORD\r\nAn index into ${COMP_WORDS} of the word containing the current cursor position. This variable is\r\navailable only in shell functions invoked by the programmable completion facilities (see Programmable\r\nCompletion below).\r\nCOMP_KEY\r\nThe key (or final key of a key sequence) used to invoke the current completion function.\r\nCOMP_LINE\r\nThe current command line. This variable is available only in shell functions and external commands\r\ninvoked by the programmable completion facilities (see Programmable Completion below).\r\nCOMP_POINT\r\nThe index of the current cursor position relative to the beginning of the current command. If the current\r\ncursor position is at the end of the current command, the value of this variable is equal to\r\n${#COMP_LINE}. This variable is available only in shell functions and external commands invoked by\r\nthe programmable completion facilities (see Programmable Completion below).\r\nCOMP_TYPE\r\nSet to an integer value corresponding to the type of completion attempted that caused a completion\r\nfunction to be called: TAB, for normal completion, ?, for listing completions after successive tabs, !, for\r\nlisting alternatives on partial word completion, @, to list completions if the word is not unmodified, or %,\r\nfor menu completion. This variable is available only in shell functions and external commands invoked by\r\nthe programmable completion facilities (see Programmable Completion below).\r\nCOMP_WORDBREAKS\r\nThe set of characters that the readline library treats as word separators when performing word completion.\r\nIf COMP_WORDBREAKS is unset, it loses its special properties, even if it is subsequently reset.\r\nCOMP_WORDS\r\nAn array variable (see Arrays below) consisting of the individual words in the current command line. The\r\nline is split into words as readline would split it, using COMP_WORDBREAKS as described above. This\r\nvariable is available only in shell functions invoked by the programmable completion facilities (see\r\nProgrammable Completion below).\r\nDIRSTACK\r\nAn array variable (see Arrays below) containing the current contents of the directory stack. Directories\r\nappear in the stack in the order they are displayed by the dirs builtin. Assigning to members of this array\r\nvariable may be used to modify directories already in the stack, but the pushd and popd builtins must be\r\nused to add and remove directories. Assignment to this variable will not change the current directory. If\r\nDIRSTACK is unset, it loses its special properties, even if it is subsequently reset.\r\nhttps://linux.die.net/man/1/bash\r\nPage 16 of 107\n\nEUID\r\nExpands to the effective user ID of the current user, initialized at shell startup. This variable is readonly.\r\nFUNCNAME\r\nAn array variable containing the names of all shell functions currently in the execution call stack. The\r\nelement with index 0 is the name of any currently-executing shell function. The bottom-most element is\r\n\"main\". This variable exists only when a shell function is executing. Assignments to FUNCNAME have no\r\neffect and return an error status. If FUNCNAME is unset, it loses its special properties, even if it is\r\nsubsequently reset.\r\nGROUPS\r\nAn array variable containing the list of groups of which the current user is a member. Assignments to GROUPS\r\nhave no effect and return an error status. If GROUPS is unset, it loses its special properties, even if it is\r\nsubsequently reset.\r\nHISTCMD\r\nThe history number, or index in the history list, of the current command. If HISTCMD is unset, it loses its\r\nspecial properties, even if it is subsequently reset.\r\nHOSTNAME\r\nAutomatically set to the name of the current host.\r\nHOSTTYPE\r\nAutomatically set to a string that uniquely describes the type of machine on which bash is executing. The\r\ndefault is system-dependent.\r\nLINENO\r\nEach time this parameter is referenced, the shell substitutes a decimal number representing the current sequential\r\nline number (starting with 1) within a script or function. When not in a script or function, the value substituted is\r\nnot guaranteed to be meaningful. If LINENO is unset, it loses its special properties, even if it is subsequently reset.\r\nMACHTYPE\r\nAutomatically set to a string that fully describes the system type on which bash is executing, in the\r\nstandard GNU cpu-company-system format. The default is system-dependent.\r\nOLDPWD\r\nThe previous working directory as set by the cd command.\r\nOPTARG\r\nThe value of the last option argument processed by the getopts builtin command (see SHELL BUILTIN\r\nCOMMANDS below).\r\nOPTIND\r\nThe index of the next argument to be processed by the getopts builtin command (see SHELL BUILTIN COMMANDS\r\nbelow).\r\nhttps://linux.die.net/man/1/bash\r\nPage 17 of 107\n\nOSTYPE\r\nAutomatically set to a string that describes the operating system on which bash is executing. The default is\r\nsystem-dependent.\r\nPIPESTATUS\r\nAn array variable (see Arrays below) containing a list of exit status values from the processes in the most-recently-executed foreground pipeline (which may contain only a single command).\r\nPPID\r\nThe process ID of the shell's parent. This variable is readonly.\r\nPWD\r\nThe current working directory as set by the cd command.\r\nRANDOM\r\nEach time this parameter is referenced, a random integer between 0 and 32767 is generated. The sequence of\r\nrandom numbers may be initialized by assigning a value to RANDOM. If RANDOM is unset, it loses its special\r\nproperties, even if it is subsequently reset.\r\nREPLY\r\nSet to the line of input read by the read builtin command when no arguments are supplied.\r\nSECONDS\r\nEach time this parameter is referenced, the number of seconds since shell invocation is returned. If a value\r\nis assigned to SECONDS, the value returned upon subsequent references is the number of seconds since the\r\nassignment plus the value assigned. If SECONDS is unset, it loses its special properties, even if it is\r\nsubsequently reset.\r\nSHELLOPTS\r\nA colon-separated list of enabled shell options. Each word in the list is a valid argument for the -o option to\r\nthe set builtin command (see SHELL BUILTIN COMMANDS below). The options appearing in SHELLOPTS\r\nare those reported as on by set -o. If this variable is in the environment when bash starts up, each shell\r\noption in the list will be enabled before reading any startup files. This variable is read-only.\r\nSHLVL\r\nIncremented by one each time an instance of bash is started.\r\nUID\r\nExpands to the user ID of the current user, initialized at shell startup. This variable is readonly.\r\nThe following variables are used by the shell. In some cases, bash assigns a default value to a variable; these\r\ncases are noted below.\r\nBASH_ENV\r\nhttps://linux.die.net/man/1/bash\r\nPage 18 of 107\n\nIf this parameter is set when bash is executing a shell script, its value is interpreted as a filename\r\ncontaining commands to initialize the shell, as in ~/.bashrc. The value of BASH_ENV is subjected to\r\nparameter expansion, command substitution, and arithmetic expansion before being interpreted as a file\r\nname. PATH is not used to search for the resultant file name.\r\nCDPATH\r\nThe search path for the cd command. This is a colon-separated list of directories in which the shell looks for\r\ndestination directories specified by the cd command. A sample value is \".:~:/usr\".\r\nBASH_XTRACEFD\r\nIf set to an integer corresponding to a valid file descriptor, bash will write the trace output generated when\r\nset -x is enabled to that file descriptor. The file descriptor is closed when BASH_XTRACEFD is unset or\r\nassigned a new value. Unsetting BASH_XTRACEFD or assigning it the empty string causes the trace output\r\nto be sent to the standard error. Note that setting BASH_XTRACEFD to 2 (the standard error file descriptor)\r\nand then unsetting it will result in the standard error being closed.\r\nCOLUMNS\r\nUsed by the select builtin command to determine the terminal width when printing selection lists.\r\nAutomatically set upon receipt of a SIGWINCH.\r\nCOMPREPLY\r\nAn array variable from which bash reads the possible completions generated by a shell function invoked\r\nby the programmable completion facility (see Programmable Completion below).\r\nEMACS\r\nIf bash finds this variable in the environment when the shell starts with value \"t\", it assumes that the shell is\r\nrunning in an emacs shell buffer and disables line editing.\r\nFCEDIT\r\nThe default editor for the fc builtin command.\r\nFIGNORE\r\nA colon-separated list of suffixes to ignore when performing filename completion (see READLINE below).\r\nA filename whose suffix matches one of the entries in FIGNORE is excluded from the list of matched\r\nfilenames. A sample value is \".o:~\".\r\nGLOBIGNORE\r\nA colon-separated list of patterns defining the set of filenames to be ignored by pathname expansion. If a\r\nfilename matched by a pathname expansion pattern also matches one of the patterns in GLOBIGNORE, it is\r\nremoved from the list of matches.\r\nHISTCONTROL\r\nA colon-separated list of values controlling how commands are saved on the history list. If the list of values\r\nincludes ignorespace, lines which begin with a space character are not saved in the history list. A value of\r\nignoredups causes lines matching the previous history entry to not be saved. A value of ignoreboth is\r\nshorthand for ignorespace and ignoredups. A value of erasedups causes all previous lines matching the\r\ncurrent line to be removed from the history list before that line is saved. Any value not in the above list is\r\nhttps://linux.die.net/man/1/bash\r\nPage 19 of 107\n\nignored. If HISTCONTROL is unset, or does not include a valid value, all lines read by the shell parser are\r\nsaved on the history list, subject to the value of HISTIGNORE. The second and subsequent lines of a multi-line compound command are not tested, and are added to the history regardless of the value of\r\nHISTCONTROL.\r\nHISTFILE\r\nThe name of the file in which command history is saved (see HISTORY below). The default value is\r\n~/.bash_history. If unset, the command history is not saved when an interactive shell exits.\r\nHISTFILESIZE\r\nThe maximum number of lines contained in the history file. When this variable is assigned a value, the\r\nhistory file is truncated, if necessary, by removing the oldest entries, to contain no more than that number\r\nof lines. The default value is 500. The history file is also truncated to this size after writing it when an\r\ninteractive shell exits.\r\nHISTIGNORE\r\nA colon-separated list of patterns used to decide which command lines should be saved on the history list.\r\nEach pattern is anchored at the beginning of the line and must match the complete line (no implicit '*' is\r\nappended). Each pattern is tested against the line after the checks specified by HISTCONTROL are applied.\r\nIn addition to the normal shell pattern matching characters, '\u0026' matches the previous history line. '\u0026' may\r\nbe escaped using a backslash; the backslash is removed before attempting a match. The second and\r\nsubsequent lines of a multi-line compound command are not tested, and are added to the history regardless\r\nof the value of HISTIGNORE.\r\nHISTSIZE\r\nThe number of commands to remember in the command history (see HISTORY below). The default value is\r\n500.\r\nHISTTIMEFORMAT\r\nIf this variable is set and not null, its value is used as a format string for strftime(3) to print the time stamp\r\nassociated with each history entry displayed by the history builtin. If this variable is set, time stamps are\r\nwritten to the history file so they may be preserved across shell sessions. This uses the history comment\r\ncharacter to distinguish timestamps from other history lines.\r\nHOME\r\nThe home directory of the current user; the default argument for the cd builtin command. The value of this\r\nvariable is also used when performing tilde expansion.\r\nHOSTFILE\r\nContains the name of a file in the same format as /etc/hosts that should be read when the shell needs to\r\ncomplete a hostname. The list of possible hostname completions may be changed while the shell is\r\nrunning; the next time hostname completion is attempted after the value is changed, bash adds the contents\r\nof the new file to the existing list. If HOSTFILE is set, but has no value, or does not name a readable file,\r\nbash attempts to read /etc/hosts to obtain the list of possible hostname completions. When HOSTFILE is\r\nunset, the hostname list is cleared.\r\nIFS\r\nhttps://linux.die.net/man/1/bash\r\nPage 20 of 107\n\nThe Internal Field Separator that is used for word splitting after expansion and to split lines into words with the\r\nread builtin command. The default value is ''\u003cspace\u003e\u003ctab\u003e\u003cnewline\u003e''.\r\nIGNOREEOF\r\nControls the action of an interactive shell on receipt of an EOF character as the sole input. If set, the value\r\nis the number of consecutive EOF characters which must be typed as the first characters on an input line\r\nbefore bash exits. If the variable exists but does not have a numeric value, or has no value, the default\r\nvalue is 10. If it does not exist, EOF signifies the end of input to the shell.\r\nINPUTRC\r\nThe filename for the readline startup file, overriding the default of ~/.inputrc (see READLINE below).\r\nLANG\r\nUsed to determine the locale category for any category not specifically selected with a variable starting with LC_.\r\nLC_ALL\r\nThis variable overrides the value of LANG and any other LC_ variable specifying a locale category.\r\nLC_COLLATE\r\nThis variable determines the collation order used when sorting the results of pathname expansion, and\r\ndetermines the behavior of range expressions, equivalence classes, and collating sequences within\r\npathname expansion and pattern matching.\r\nLC_CTYPE\r\nThis variable determines the interpretation of characters and the behavior of character classes within\r\npathname expansion and pattern matching.\r\nLC_MESSAGES\r\nThis variable determines the locale used to translate double-quoted strings preceded by a $.\r\nLC_NUMERIC\r\nThis variable determines the locale category used for number formatting.\r\nLINES\r\nUsed by the select builtin command to determine the column length for printing selection lists. Automatically set\r\nupon receipt of a SIGWINCH.\r\nMAIL\r\nIf this parameter is set to a file name and the MAILPATH variable is not set, bash informs the user of the arrival of\r\nmail in the specified file.\r\nMAILCHECK\r\nSpecifies how often (in seconds) bash checks for mail. The default is 60 seconds. When it is time to check\r\nfor mail, the shell does so before displaying the primary prompt. If this variable is unset, or set to a value\r\nthat is not a number greater than or equal to zero, the shell disables mail checking.\r\nMAILPATH\r\nA colon-separated list of file names to be checked for mail. The message to be printed when mail arrives in\r\na particular file may be specified by separating the file name from the message with a '?'. When used in the\r\nhttps://linux.die.net/man/1/bash\r\nPage 21 of 107\n\ntext of the message, $_ expands to the name of the current mailfile. Example:\r\nMAILPATH='/var/mail/bfox?\"You have mail\":~/shell-mail?\"$_ has mail!\"'\r\nBash supplies a default value for this variable, but the location of the user mail files that it uses is system\r\ndependent (e.g., /var/mail/$USER).\r\nOPTERR\r\nIf set to the value 1, bash displays error messages generated by the getopts builtin command (see SHELL BUILTIN\r\nCOMMANDS below). OPTERR is initialized to 1 each time the shell is invoked or a shell script is executed.\r\nPATH\r\nThe search path for commands. It is a colon-separated list of directories in which the shell looks for commands\r\n(see COMMAND EXECUTION below). A zero-length (null) directory name in the value of PATH indicates the\r\ncurrent directory. A null directory name may appear as two adjacent colons, or as an initial or trailing colon. The\r\ndefault path is system-dependent, and is set by the administrator who installs bash. A common value is\r\n''/usr/gnu/bin:/usr/local/bin:/usr/ucb:/bin:/usr/bin''.\r\nPOSIXLY_CORRECT\r\nIf this variable is in the environment when bash starts, the shell enters posix mode before reading the\r\nstartup files, as if the --posix invocation option had been supplied. If it is set while the shell is running,\r\nbash enables posix mode, as if the command set -o posix had been executed.\r\nPROMPT_COMMAND\r\nIf set, the value is executed as a command prior to issuing each primary prompt.\r\nPROMPT_DIRTRIM\r\nIf set to a number greater than zero, the value is used as the number of trailing directory components to\r\nretain when expanding the \\w and \\W prompt string escapes (see PROMPTING below). Characters removed\r\nare replaced with an ellipsis.\r\nPS1\r\nThe value of this parameter is expanded (see PROMPTING below) and used as the primary prompt string. The\r\ndefault value is ''\\s-\\v\\$ ''.\r\nPS2\r\nThe value of this parameter is expanded as with PS1 and used as the secondary prompt string. The default is ''\u003e ''.\r\nPS3\r\nThe value of this parameter is used as the prompt for the select command (see SHELL GRAMMAR above).\r\nPS4\r\nThe value of this parameter is expanded as with PS1 and the value is printed before each command bash displays\r\nduring an execution trace. The first character of PS4 is replicated multiple times, as necessary, to indicate multiple\r\nlevels of indirection. The default is ''+ ''.\r\nSHELL\r\nhttps://linux.die.net/man/1/bash\r\nPage 22 of 107\n\nThe full pathname to the shell is kept in this environment variable. If it is not set when the shell starts, bash\r\nassigns to it the full pathname of the current user's login shell.\r\nTIMEFORMAT\r\nThe value of this parameter is used as a format string specifying how the timing information for pipelines\r\nprefixed with the time reserved word should be displayed. The % character introduces an escape sequence\r\nthat is expanded to a time value or other information. The escape sequences and their meanings are as\r\nfollows; the braces denote optional portions.\r\n%%\r\nA literal %.\r\n%[p][l]R\r\nThe elapsed time in seconds.\r\n%[p][l]U\r\nThe number of CPU seconds spent in user mode.\r\n%[p][l]S\r\nThe number of CPU seconds spent in system mode.\r\n%P\r\nThe CPU percentage, computed as (%U + %S) / %R.\r\nThe optional p is a digit specifying the precision, the number of fractional digits after a decimal point. A\r\nvalue of 0 causes no decimal point or fraction to be output. At most three places after the decimal point\r\nmay be specified; values of p greater than 3 are changed to 3. If p is not specified, the value 3 is used.\r\nThe optional l specifies a longer format, including minutes, of the form MMmSS.FFs. The value of p\r\ndetermines whether or not the fraction is included.\r\nIf this variable is not set, bash acts as if it had the value $'\\nreal\\t%3lR\\nuser\\t%3lU\\nsys%3lS'. If the\r\nvalue is null, no timing information is displayed. A trailing newline is added when the format string is\r\ndisplayed.\r\nTMOUT\r\nIf set to a value greater than zero, TMOUT is treated as the default timeout for the read builtin. The select\r\ncommand terminates if input does not arrive after TMOUT seconds when input is coming from a terminal. In an\r\ninteractive shell, the value is interpreted as the number of seconds to wait for input after issuing the primary\r\nprompt. Bash terminates after waiting for that number of seconds if input does not arrive.\r\nTMPDIR\r\nIf set, Bash uses its value as the name of a directory in which Bash creates temporary files for the shell's use.\r\nhttps://linux.die.net/man/1/bash\r\nPage 23 of 107\n\nauto_resume\r\nThis variable controls how the shell interacts with the user and job control. If this variable is set, single\r\nword simple commands without redirections are treated as candidates for resumption of an existing stopped\r\njob. There is no ambiguity allowed; if there is more than one job beginning with the string typed, the job\r\nmost recently accessed is selected. The name of a stopped job, in this context, is the command line used to\r\nstart it. If set to the value exact, the string supplied must match the name of a stopped job exactly; if set to\r\nsubstring, the string supplied needs to match a substring of the name of a stopped job. The substring value\r\nprovides functionality analogous to the %? job identifier (see JOB CONTROL below). If set to any other\r\nvalue, the supplied string must be a prefix of a stopped job's name; this provides functionality analogous to\r\nthe %string job identifier.\r\nhistchars\r\nThe two or three characters which control history expansion and tokenization (see HISTORY EXPANSION\r\nbelow). The first character is the history expansion character, the character which signals the start of a\r\nhistory expansion, normally '!'. The second character is the quick substitution character, which is used as\r\nshorthand for re-running the previous command entered, substituting one string for another in the\r\ncommand. The default is '^'. The optional third character is the character which indicates that the remainder\r\nof the line is a comment when found as the first character of a word, normally '#'. The history comment\r\ncharacter causes history substitution to be skipped for the remaining words on the line. It does not\r\nnecessarily cause the shell parser to treat the rest of the line as a comment.\r\nArrays\r\nBash provides one-dimensional indexed and associative array variables. Any variable may be used as an indexed\r\narray; the declare builtin will explicitly declare an array. There is no maximum limit on the size of an array, nor\r\nany requirement that members be indexed or assigned contiguously. Indexed arrays are referenced using integers\r\n(including arithmetic expressions) and are zero-based; associative arrays are referenced using arbitrary strings.\r\nAn indexed array is created automatically if any variable is assigned to using the syntax name[subscript]=value.\r\nThe subscript is treated as an arithmetic expression that must evaluate to a number greater than or equal to zero.\r\nTo explicitly declare an indexed array, use declare -a name (see SHELL BUILTIN COMMANDS below). declare -a\r\nname[subscript] is also accepted; the subscript is ignored.\r\nAssociative arrays are created using declare -A name.\r\nAttributes may be specified for an array variable using the declare and readonly builtins. Each attribute applies to\r\nall members of an array.\r\nArrays are assigned to using compound assignments of the form name=(value1 ... valuen), where each value is of\r\nthe form [subscript]=string. Indexed array assignments do not require the bracket and subscript. When assigning\r\nto indexed arrays, if the optional brackets and subscript are supplied, that index is assigned to; otherwise the index\r\nof the element assigned is the last index assigned to by the statement plus one. Indexing starts at zero.\r\nWhen assigning to an associative array, the subscript is required.\r\nhttps://linux.die.net/man/1/bash\r\nPage 24 of 107\n\nThis syntax is also accepted by the declare builtin. Individual array elements may be assigned to using the\r\nname[subscript]=value syntax introduced above.\r\nAny element of an array may be referenced using ${name[subscript]}. The braces are required to avoid conflicts\r\nwith pathname expansion. If subscript is @ or *, the word expands to all members of name. These subscripts\r\ndiffer only when the word appears within double quotes. If the word is double-quoted, ${name[*]} expands to a\r\nsingle word with the value of each array member separated by the first character of the IFS special variable, and\r\n${name[@]} expands each element of name to a separate word. When there are no array members, ${name[@]}\r\nexpands to nothing. If the double-quoted expansion occurs within a word, the expansion of the first parameter is\r\njoined with the beginning part of the original word, and the expansion of the last parameter is joined with the last\r\npart of the original word. This is analogous to the expansion of the special parameters * and @ (see Special\r\nParameters above). ${#name[subscript]} expands to the length of ${name[subscript]}. If subscript is * or @, the\r\nexpansion is the number of elements in the array. Referencing an array variable without a subscript is equivalent\r\nto referencing the array with a subscript of 0.\r\nAn array variable is considered set if a subscript has been assigned a value. The null string is a valid value.\r\nThe unset builtin is used to destroy arrays. unset name[subscript] destroys the array element at index subscript.\r\nCare must be taken to avoid unwanted side effects caused by pathname expansion. unset name, where name is an\r\narray, or unset name[subscript], where subscript is * or @, removes the entire array.\r\nThe declare, local, and readonly builtins each accept a -a option to specify an indexed array and a -A option to\r\nspecify an associative array. The read builtin accepts a -a option to assign a list of words read from the standard\r\ninput to an array. The set and declare builtins display array values in a way that allows them to be reused as\r\nassignments.\r\nExpansion\r\nExpansion is performed on the command line after it has been split into words. There are seven kinds of expansion\r\nperformed: brace expansion, tilde expansion, parameter and variable expansion, command substitution,\r\narithmetic expansion, word splitting, and pathname expansion.\r\nThe order of expansions is: brace expansion, tilde expansion, parameter, variable and arithmetic expansion and\r\ncommand substitution (done in a left-to-right fashion), word splitting, and pathname expansion.\r\nOn systems that can support it, there is an additional expansion available: process substitution.\r\nOnly brace expansion, word splitting, and pathname expansion can change the number of words of the expansion;\r\nother expansions expand a single word to a single word. The only exceptions to this are the expansions of \"$@\"\r\nand \"${name[@]}\" as explained above (see PARAMETERS).\r\nBrace Expansion\r\nBrace expansion is a mechanism by which arbitrary strings may be generated. This mechanism is similar to\r\npathname expansion, but the filenames generated need not exist. Patterns to be brace expanded take the form of an\r\noptional preamble, followed by either a series of comma-separated strings or a sequence expression between a pair\r\nhttps://linux.die.net/man/1/bash\r\nPage 25 of 107\n\nof braces, followed by an optional postscript. The preamble is prefixed to each string contained within the braces,\r\nand the postscript is then appended to each resulting string, expanding left to right.\r\nBrace expansions may be nested. The results of each expanded string are not sorted; left to right order is\r\npreserved. For example, a{d,c,b}e expands into 'ade ace abe'.\r\nA sequence expression takes the form {x..y[..incr]}, where x and y are either integers or single characters, and incr,\r\nan optional increment, is an integer. When integers are supplied, the expression expands to each number between x\r\nand y, inclusive. Supplied integers may be prefixed with 0 to force each term to have the same width. When either\r\nx or y begins with a zero, the shell attempts to force all generated terms to contain the same number of digits, zero-padding where necessary. When characters are supplied, the expression expands to each character\r\nlexicographically between x and y, inclusive. Note that both x and y must be of the same type. When the increment\r\nis supplied, it is used as the difference between each term. The default increment is 1 or -1 as appropriate.\r\nBrace expansion is performed before any other expansions, and any characters special to other expansions are\r\npreserved in the result. It is strictly textual. Bash does not apply any syntactic interpretation to the context of the\r\nexpansion or the text between the braces.\r\nA correctly-formed brace expansion must contain unquoted opening and closing braces, and at least one unquoted\r\ncomma or a valid sequence expression. Any incorrectly formed brace expansion is left unchanged. A { or , may be\r\nquoted with a backslash to prevent its being considered part of a brace expression. To avoid conflicts with\r\nparameter expansion, the string ${ is not considered eligible for brace expansion.\r\nThis construct is typically used as shorthand when the common prefix of the strings to be generated is longer than\r\nin the above example:\r\nmkdir /usr/local/src/bash/{old,new,dist,bugs}\r\nor\r\nchown root /usr/{ucb/{ex,edit},lib/{ex?.?*,how_ex}}\r\nBrace expansion introduces a slight incompatibility with historical versions of sh. sh does not treat opening or\r\nclosing braces specially when they appear as part of a word, and preserves them in the output. Bash removes\r\nbraces from words as a consequence of brace expansion. For example, a word entered to sh as file{1,2} appears\r\nidentically in the output. The same word is output as file1 file2 after expansion by bash. If strict compatibility\r\nwith sh is desired, start bash with the +B option or disable brace expansion with the +B option to the set\r\ncommand (see SHELL BUILTIN COMMANDS below).\r\nTilde Expansion\r\nIf a word begins with an unquoted tilde character ('~'), all of the characters preceding the first unquoted slash (or\r\nall characters, if there is no unquoted slash) are considered a tilde-prefix. If none of the characters in the tilde-prefix are quoted, the characters in the tilde-prefix following the tilde are treated as a possible login name. If this\r\nlogin name is the null string, the tilde is replaced with the value of the shell parameter HOME. If HOME is unset,\r\nthe home directory of the user executing the shell is substituted instead. Otherwise, the tilde-prefix is replaced\r\nwith the home directory associated with the specified login name.\r\nhttps://linux.die.net/man/1/bash\r\nPage 26 of 107\n\nIf the tilde-prefix is a '~+', the value of the shell variable PWD replaces the tilde-prefix. If the tilde-prefix is a '~-',\r\nthe value of the shell variable OLDPWD, if it is set, is substituted. If the characters following the tilde in the tilde-prefix consist of a number N, optionally prefixed by a '+' or a '-', the tilde-prefix is replaced with the corresponding\r\nelement from the directory stack, as it would be displayed by the dirs builtin invoked with the tilde-prefix as an\r\nargument. If the characters following the tilde in the tilde-prefix consist of a number without a leading '+' or '-', '+'\r\nis assumed.\r\nIf the login name is invalid, or the tilde expansion fails, the word is unchanged.\r\nEach variable assignment is checked for unquoted tilde-prefixes immediately following a : or the first =. In these\r\ncases, tilde expansion is also performed. Consequently, one may use file names with tildes in assignments to\r\nPATH, MAILPATH, and CDPATH, and the shell assigns the expanded value.\r\nParameter Expansion\r\nThe '$' character introduces parameter expansion, command substitution, or arithmetic expansion. The parameter\r\nname or symbol to be expanded may be enclosed in braces, which are optional but serve to protect the variable to\r\nbe expanded from characters immediately following it which could be interpreted as part of the name.\r\nWhen braces are used, the matching ending brace is the first '}' not escaped by a backslash or within a quoted\r\nstring, and not within an embedded arithmetic expansion, command substitution, or parameter expansion.\r\n${parameter}\r\nThe value of parameter is substituted. The braces are required when parameter is a positional parameter\r\nwith more than one digit, or when parameter is followed by a character which is not to be interpreted as\r\npart of its name.\r\nIf the first character of parameter is an exclamation point (!), a level of variable indirection is introduced. Bash\r\nuses the value of the variable formed from the rest of parameter as the name of the variable; this variable is then\r\nexpanded and that value is used in the rest of the substitution, rather than the value of parameter itself. This is\r\nknown as indirect expansion. The exceptions to this are the expansions of ${!prefix*} and ${!name[@]} described\r\nbelow. The exclamation point must immediately follow the left brace in order to introduce indirection.\r\nIn each of the cases below, word is subject to tilde expansion, parameter expansion, command substitution, and\r\narithmetic expansion.\r\nWhen not performing substring expansion, using the forms documented below, bash tests for a parameter that is\r\nunset or null. Omitting the colon results in a test only for a parameter that is unset.\r\n${parameter:-word}\r\nUse Default Values. If parameter is unset or null, the expansion of word is substituted. Otherwise, the\r\nvalue of parameter is substituted.\r\n${parameter:=word}\r\nAssign Default Values. If parameter is unset or null, the expansion of word is assigned to parameter. The\r\nvalue of parameter is then substituted. Positional parameters and special parameters may not be assigned to\r\nin this way.\r\n${parameter:?word}\r\nhttps://linux.die.net/man/1/bash\r\nPage 27 of 107\n\nDisplay Error if Null or Unset. If parameter is null or unset, the expansion of word (or a message to that\r\neffect if word is not present) is written to the standard error and the shell, if it is not interactive, exits.\r\nOtherwise, the value of parameter is substituted.\r\n${parameter:+word}\r\nUse Alternate Value. If parameter is null or unset, nothing is substituted, otherwise the expansion of word\r\nis substituted.\r\n${parameter:offset}\r\n${parameter:offset:length}\r\nSubstring Expansion. Expands to up to length characters of parameter starting at the character specified\r\nby offset. If length is omitted, expands to the substring of parameter starting at the character specified by\r\noffset. length and offset are arithmetic expressions (see ARITHMETIC EVALUATION below). length must\r\nevaluate to a number greater than or equal to zero. If offset evaluates to a number less than zero, the value\r\nis used as an offset from the end of the value of parameter. If parameter is @, the result is length\r\npositional parameters beginning at offset. If parameter is an indexed array name subscripted by @ or *, the\r\nresult is the length members of the array beginning with ${parameter[offset]}. A negative offset is taken\r\nrelative to one greater than the maximum index of the specified array. Substring expansion applied to an\r\nassociative array produces undefined results. Note that a negative offset must be separated from the colon\r\nby at least one space to avoid being confused with the :- expansion. Substring indexing is zero-based unless\r\nthe positional parameters are used, in which case the indexing starts at 1 by default. If offset is 0, and the\r\npositional parameters are used, $0 is prefixed to the list.\r\n${!prefix*}\r\n${!prefix@}\r\nNames matching prefix. Expands to the names of variables whose names begin with prefix, separated by\r\nthe first character of the IFS special variable. When @ is used and the expansion appears within double\r\nquotes, each variable name expands to a separate word.\r\n${!name[@]}\r\n${!name[*]}\r\nList of array keys. If name is an array variable, expands to the list of array indices (keys) assigned in\r\nname. If name is not an array, expands to 0 if name is set and null otherwise. When @ is used and the\r\nexpansion appears within double quotes, each key expands to a separate word.\r\n${#parameter}\r\nParameter length. The length in characters of the value of parameter is substituted. If parameter is * or\r\n@, the value substituted is the number of positional parameters. If parameter is an array name subscripted\r\nby * or @, the value substituted is the number of elements in the array.\r\n${parameter#word}\r\n${parameter##word}\r\nRemove matching prefix pattern. The word is expanded to produce a pattern just as in pathname\r\nexpansion. If the pattern matches the beginning of the value of parameter, then the result of the expansion\r\nis the expanded value of parameter with the shortest matching pattern (the ''#'' case) or the longest\r\nmatching pattern (the ''##'' case) deleted. If parameter is @ or *, the pattern removal operation is applied to\r\neach positional parameter in turn, and the expansion is the resultant list. If parameter is an array variable\r\nhttps://linux.die.net/man/1/bash\r\nPage 28 of 107\n\nsubscripted with @ or *, the pattern removal operation is applied to each member of the array in turn, and\r\nthe expansion is the resultant list.\r\n${parameter%word}\r\n${parameter%%word}\r\nRemove matching suffix pattern. The word is expanded to produce a pattern just as in pathname\r\nexpansion. If the pattern matches a trailing portion of the expanded value of parameter, then the result of\r\nthe expansion is the expanded value of parameter with the shortest matching pattern (the ''%'' case) or the\r\nlongest matching pattern (the ''%%'' case) deleted. If parameter is @ or *, the pattern removal operation is\r\napplied to each positional parameter in turn, and the expansion is the resultant list. If parameter is an array\r\nvariable subscripted with @ or *, the pattern removal operation is applied to each member of the array in\r\nturn, and the expansion is the resultant list.\r\n${parameter/pattern/string}\r\nPattern substitution. The pattern is expanded to produce a pattern just as in pathname expansion.\r\nParameter is expanded and the longest match of pattern against its value is replaced with string. If pattern\r\nbegins with /, all matches of pattern are replaced with string. Normally only the first match is replaced. If\r\npattern begins with #, it must match at the beginning of the expanded value of parameter. If pattern begins\r\nwith %, it must match at the end of the expanded value of parameter. If string is null, matches of pattern\r\nare deleted and the / following pattern may be omitted. If parameter is @ or *, the substitution operation is\r\napplied to each positional parameter in turn, and the expansion is the resultant list. If parameter is an array\r\nvariable subscripted with @ or *, the substitution operation is applied to each member of the array in turn,\r\nand the expansion is the resultant list.\r\n${parameter^pattern}\r\n${parameter^^pattern}\r\n${parameter,pattern}\r\n${parameter,,pattern}\r\nCase modification. This expansion modifies the case of alphabetic characters in parameter. The pattern is\r\nexpanded to produce a pattern just as in pathname expansion. The ^ operator converts lowercase letters\r\nmatching pattern to uppercase; the , operator converts matching uppercase letters to lowercase. The ^^ and\r\n,, expansions convert each matched character in the expanded value; the ^ and , expansions match and\r\nconvert only the first character in the expanded value.. If pattern is omitted, it is treated like a ?, which\r\nmatches every character. If parameter is @ or *, the case modification operation is applied to each\r\npositional parameter in turn, and the expansion is the resultant list. If parameter is an array variable\r\nsubscripted with @ or *, the case modification operation is applied to each member of the array in turn,\r\nand the expansion is the resultant list.\r\nCommand Substitution\r\nCommand substitution allows the output of a command to replace the command name. There are two forms:\r\n$(command)\r\nor\r\n`command`\r\nBash performs the expansion by executing command and replacing the command substitution with the standard\r\noutput of the command, with any trailing newlines deleted. Embedded newlines are not deleted, but they may be\r\nhttps://linux.die.net/man/1/bash\r\nPage 29 of 107\n\nremoved during word splitting. The command substitution $(cat file) can be replaced by the equivalent but faster\r\n$(\u003c file).\r\nWhen the old-style backquote form of substitution is used, backslash retains its literal meaning except when\r\nfollowed by $, `, or \\. The first backquote not preceded by a backslash terminates the command substitution. When\r\nusing the $(command) form, all characters between the parentheses make up the command; none are treated\r\nspecially.\r\nCommand substitutions may be nested. To nest when using the backquoted form, escape the inner backquotes with\r\nbackslashes.\r\nIf the substitution appears within double quotes, word splitting and pathname expansion are not performed on the\r\nresults.\r\nArithmetic Expansion\r\nArithmetic expansion allows the evaluation of an arithmetic expression and the substitution of the result. The\r\nformat for arithmetic expansion is:\r\n$((expression))\r\nThe expression is treated as if it were within double quotes, but a double quote inside the parentheses is not treated\r\nspecially. All tokens in the expression undergo parameter expansion, string expansion, command substitution, and\r\nquote removal. Arithmetic expansions may be nested.\r\nThe evaluation is performed according to the rules listed below under ARITHMETIC EVALUATION. If expression is\r\ninvalid, bash prints a message indicating failure and no substitution occurs.\r\nProcess Substitution\r\nProcess substitution is supported on systems that support named pipes (FIFOs) or the /dev/fd method of naming\r\nopen files. It takes the form of \u003c(list) or \u003e(list). The process list is run with its input or output connected to a FIFO\r\nor some file in /dev/fd. The name of this file is passed as an argument to the current command as the result of the\r\nexpansion. If the \u003e(list) form is used, writing to the file will provide input for list. If the \u003c(list) form is used, the\r\nfile passed as an argument should be read to obtain the output of list.\r\nWhen available, process substitution is performed simultaneously with parameter and variable expansion,\r\ncommand substitution, and arithmetic expansion.\r\nWord Splitting\r\nThe shell scans the results of parameter expansion, command substitution, and arithmetic expansion that did not\r\noccur within double quotes for word splitting.\r\nThe shell treats each character of IFS as a delimiter, and splits the results of the other expansions into words on\r\nthese characters. If IFS is unset, or its value is exactly \u003cspace\u003e\u003ctab\u003e\u003cnewline\u003e, the default, then sequences of\r\n\u003cspace\u003e, \u003ctab\u003e, and \u003cnewline\u003e at the beginning and end of the results of the previous expansions are ignored,\r\nand any sequence of IFS characters not at the beginning or end serves to delimit words. If IFS has a value other\r\nthan the default, then sequences of the whitespace characters space and tab are ignored at the beginning and end\r\nhttps://linux.die.net/man/1/bash\r\nPage 30 of 107\n\nof the word, as long as the whitespace character is in the value of IFS (an IFS whitespace character). Any character\r\nin IFS that is not IFS whitespace, along with any adjacent IFS whitespace characters, delimits a field. A sequence\r\nof IFS whitespace characters is also treated as a delimiter. If the value of IFS is null, no word splitting occurs.\r\nExplicit null arguments (\"\" or '') are retained. Unquoted implicit null arguments, resulting from the expansion of\r\nparameters that have no values, are removed. If a parameter with no value is expanded within double quotes, a\r\nnull argument results and is retained.\r\nNote that if no expansion occurs, no splitting is performed.\r\nPathname Expansion\r\nAfter word splitting, unless the -f option has been set, bash scans each word for the characters *, ?, and [. If one\r\nof these characters appears, then the word is regarded as a pattern, and replaced with an alphabetically sorted list\r\nof file names matching the pattern. If no matching file names are found, and the shell option nullglob is not\r\nenabled, the word is left unchanged. If the nullglob option is set, and no matches are found, the word is removed.\r\nIf the failglob shell option is set, and no matches are found, an error message is printed and the command is not\r\nexecuted. If the shell option nocaseglob is enabled, the match is performed without regard to the case of\r\nalphabetic characters. When a pattern is used for pathname expansion, the character ''.'' at the start of a name or\r\nimmediately following a slash must be matched explicitly, unless the shell option dotglob is set. When matching a\r\npathname, the slash character must always be matched explicitly. In other cases, the ''.'' character is not treated\r\nspecially. See the description of shopt below under SHELL BUILTIN COMMANDS for a description of the\r\nnocaseglob, nullglob, failglob, and dotglob shell options.\r\nThe GLOBIGNORE shell variable may be used to restrict the set of file names matching a pattern. If GLOBIGNORE\r\nis set, each matching file name that also matches one of the patterns in GLOBIGNORE is removed from the list of\r\nmatches. The file names ''.'' and ''..'' are always ignored when GLOBIGNORE is set and not null. However, setting\r\nGLOBIGNORE to a non-null value has the effect of enabling the dotglob shell option, so all other file names\r\nbeginning with a ''.'' will match. To get the old behavior of ignoring file names beginning with a ''.'', make ''.*''\r\none of the patterns in GLOBIGNORE. The dotglob option is disabled when GLOBIGNORE is unset.\r\nPattern Matching\r\nAny character that appears in a pattern, other than the special pattern characters described below, matches itself.\r\nThe NUL character may not occur in a pattern. A backslash escapes the following character; the escaping\r\nbackslash is discarded when matching. The special pattern characters must be quoted if they are to be matched\r\nliterally.\r\nThe special pattern characters have the following meanings:\r\n*\r\nMatches any string, including the null string. When the globstar shell option is enabled, and * is used in a\r\npathname expansion context, two adjacent *s used as a single pattern will match all files and zero or more\r\ndirectories and subdirectories. If followed by a /, two adjacent *s will match only directories and subdirectories.\r\nhttps://linux.die.net/man/1/bash\r\nPage 31 of 107\n\n?\r\nMatches any single character.\r\n[...]\r\nMatches any one of the enclosed characters. A pair of characters separated by a hyphen denotes a range\r\nexpression; any character that sorts between those two characters, inclusive, using the current locale's collating\r\nsequence and character set, is matched. If the first character following the [ is a ! or a ^ then any character not\r\nenclosed is matched. The sorting order of characters in range expressions is determined by the current locale and\r\nthe value of the LC_COLLATE shell variable, if set. A - may be matched by including it as the first or last character\r\nin the set. A ] may be matched by including it as the first character in the set.\r\nWithin [ and ], character classes can be specified using the syntax [:class:], where class is one of the\r\nfollowing classes defined in the POSIX standard:\r\nalnum alpha ascii blank cntrl digit graph lower print punct space upper word xdigit\r\nA character class matches any character belonging to that class. The word character class matches letters,\r\ndigits, and the character _.\r\nWithin [ and ], an equivalence class can be specified using the syntax [=c=], which matches all characters\r\nwith the same collation weight (as defined by the current locale) as the character c.\r\nWithin [ and ], the syntax [.symbol.] matches the collating symbol symbol.\r\nIf the extglob shell option is enabled using the shopt builtin, several extended pattern matching operators are\r\nrecognized. In the following description, a pattern-list is a list of one or more patterns separated by a |. Composite\r\npatterns may be formed using one or more of the following sub-patterns:\r\n?(pattern-list)\r\nMatches zero or one occurrence of the given patterns\r\n*(pattern-list)\r\nMatches zero or more occurrences of the given patterns\r\n+(pattern-list)\r\nMatches one or more occurrences of the given patterns\r\n@(pattern-list)\r\nMatches one of the given patterns\r\n!(pattern-list)\r\nMatches anything except one of the given patterns\r\nQuote Removal\r\nhttps://linux.die.net/man/1/bash\r\nPage 32 of 107\n\nAfter the preceding expansions, all unquoted occurrences of the characters \\, ', and \" that did not result from one\r\nof the above expansions are removed.\r\nRedirection\r\nBefore a command is executed, its input and output may be redirected using a special notation interpreted by the\r\nshell. Redirection may also be used to open and close files for the current shell execution environment. The\r\nfollowing redirection operators may precede or appear anywhere within a simple command or may follow a\r\ncommand. Redirections are processed in the order they appear, from left to right.\r\nEach redirection that may be preceded by a file descriptor number may instead be preceded by a word of the form\r\n{varname}. In this case, for each redirection operator except \u003e\u0026- and \u003c\u0026-, the shell will allocate a file descriptor\r\ngreater than 10 and assign it to varname. If \u003e\u0026- or \u003c\u0026- is preceded by {varname}, the value of varname defines\r\nthe file descriptor to close.\r\nIn the following descriptions, if the file descriptor number is omitted, and the first character of the redirection\r\noperator is \u003c, the redirection refers to the standard input (file descriptor 0). If the first character of the redirection\r\noperator is \u003e, the redirection refers to the standard output (file descriptor 1).\r\nThe word following the redirection operator in the following descriptions, unless otherwise noted, is subjected to\r\nbrace expansion, tilde expansion, parameter expansion, command substitution, arithmetic expansion, quote\r\nremoval, pathname expansion, and word splitting. If it expands to more than one word, bash reports an error.\r\nNote that the order of redirections is significant. For example, the command\r\nls \u003e dirlist 2\u003e\u00261\r\ndirects both standard output and standard error to the file dirlist, while the command\r\nls 2\u003e\u00261 \u003e dirlist\r\ndirects only the standard output to file dirlist, because the standard error was duplicated from the standard output\r\nbefore the standard output was redirected to dirlist.\r\nBash handles several filenames specially when they are used in redirections, as described in the following table:\r\n/dev/fd/fd\r\nIf fd is a valid integer, file descriptor fd is duplicated.\r\n/dev/stdin\r\nFile descriptor 0 is duplicated.\r\n/dev/stdout\r\nFile descriptor 1 is duplicated.\r\n/dev/stderr\r\nFile descriptor 2 is duplicated.\r\nhttps://linux.die.net/man/1/bash\r\nPage 33 of 107\n\n/dev/tcp/host/port\r\nIf host is a valid hostname or Internet address, and port is an integer port number or service name, bash attempts\r\nto open a TCP connection to the corresponding socket.\r\n/dev/udp/host/port\r\nIf host is a valid hostname or Internet address, and port is an integer port number or service name, bash attempts\r\nto open a UDP connection to the corresponding socket.\r\nA failure to open or create a file causes the redirection to fail.\r\nRedirections using file descriptors greater than 9 should be used with care, as they may conflict with file\r\ndescriptors the shell uses internally.\r\nRedirecting Input\r\nRedirection of input causes the file whose name results from the expansion of word to be opened for reading on\r\nfile descriptor n, or the standard input (file descriptor 0) if n is not specified.\r\nThe general format for redirecting input is:\r\n[n]\u003cword\r\nRedirecting Output\r\nRedirection of output causes the file whose name results from the expansion of word to be opened for writing on\r\nfile descriptor n, or the standard output (file descriptor 1) if n is not specified. If the file does not exist it is created;\r\nif it does exist it is truncated to zero size.\r\nThe general format for redirecting output is:\r\n[n]\u003eword\r\nIf the redirection operator is \u003e, and the noclobber option to the set builtin has been enabled, the redirection will\r\nfail if the file whose name results from the expansion of word exists and is a regular file. If the redirection\r\noperator is \u003e|, or the redirection operator is \u003e and the noclobber option to the set builtin command is not enabled,\r\nthe redirection is attempted even if the file named by word exists.\r\nAppending Redirected Output\r\nRedirection of output in this fashion causes the file whose name results from the expansion of word to be opened\r\nfor appending on file descriptor n, or the standard output (file descriptor 1) if n is not specified. If the file does not\r\nexist it is created.\r\nThe general format for appending output is:\r\n[n]\u003e\u003eword\r\nRedirecting Standard Output and Standard Error\r\nhttps://linux.die.net/man/1/bash\r\nPage 34 of 107\n\nThis construct allows both the standard output (file descriptor 1) and the standard error output (file descriptor 2) to\r\nbe redirected to the file whose name is the expansion of word.\r\nThere are two formats for redirecting standard output and standard error:\r\n\u0026\u003eword\r\nand\r\n\u003e\u0026word\r\nOf the two forms, the first is preferred. This is semantically equivalent to\r\n\u003eword 2\u003e\u00261\r\nAppending Standard Output and Standard Error\r\nThis construct allows both the standard output (file descriptor 1) and the standard error output (file descriptor 2) to\r\nbe appended to the file whose name is the expansion of word.\r\nThe format for appending standard output and standard error is:\r\n\u0026\u003e\u003eword\r\nThis is semantically equivalent to\r\n\u003e\u003eword 2\u003e\u00261\r\nHere Documents\r\nThis type of redirection instructs the shell to read input from the current source until a line containing only\r\ndelimiter (with no trailing blanks) is seen. All of the lines read up to that point are then used as the standard input\r\nfor a command.\r\nThe format of here-documents is:\r\n\u003c\u003c[-]word\r\n here-document\r\ndelimiter\r\nNo parameter expansion, command substitution, arithmetic expansion, or pathname expansion is performed on\r\nword. If any characters in word are quoted, the delimiter is the result of quote removal on word, and the lines in\r\nthe here-document are not expanded. If word is unquoted, all lines of the here-document are subjected to\r\nparameter expansion, command substitution, and arithmetic expansion. In the latter case, the character sequence \\\r\n\u003cnewline\u003e is ignored, and \\ must be used to quote the characters \\, $, and `.\r\nIf the redirection operator is \u003c\u003c-, then all leading tab characters are stripped from input lines and the line\r\ncontaining delimiter. This allows here-documents within shell scripts to be indented in a natural fashion.\r\nHere Strings\r\nA variant of here documents, the format is:\r\nhttps://linux.die.net/man/1/bash\r\nPage 35 of 107\n\n\u003c\u003c\u003cword\r\nThe word is expanded and supplied to the command on its standard input.\r\nDuplicating File Descriptors\r\nThe redirection operator\r\n[n]\u003c\u0026word\r\nis used to duplicate input file descriptors. If word expands to one or more digits, the file descriptor denoted by n is\r\nmade to be a copy of that file descriptor. If the digits in word do not specify a file descriptor open for input, a\r\nredirection error occurs. If word evaluates to -, file descriptor n is closed. If n is not specified, the standard input\r\n(file descriptor 0) is used.\r\nThe operator\r\n[n]\u003e\u0026word\r\nis used similarly to duplicate output file descriptors. If n is not specified, the standard output (file descriptor 1) is\r\nused. If the digits in word do not specify a file descriptor open for output, a redirection error occurs. As a special\r\ncase, if n is omitted, and word does not expand to one or more digits, the standard output and standard error are\r\nredirected as described previously.\r\nMoving File Descriptors\r\nThe redirection operator\r\n[n]\u003c\u0026digit-moves the file descriptor digit to file descriptor n, or the standard input (file descriptor 0) if n is not specified. digit\r\nis closed after being duplicated to n.\r\nSimilarly, the redirection operator\r\n[n]\u003e\u0026digit-moves the file descriptor digit to file descriptor n, or the standard output (file descriptor 1) if n is not specified.\r\nOpening File Descriptors for Reading and Writing\r\nThe redirection operator\r\n[n]\u003c\u003eword\r\ncauses the file whose name is the expansion of word to be opened for both reading and writing on file descriptor n,\r\nor on file descriptor 0 if n is not specified. If the file does not exist, it is created.\r\nAliases\r\nAliases allow a string to be substituted for a word when it is used as the first word of a simple command. The shell\r\nmaintains a list of aliases that may be set and unset with the alias and unalias builtin commands (see SHELL\r\nBUILTIN COMMANDS below). The first word of each simple command, if unquoted, is checked to see if it has an\r\nalias. If so, that word is replaced by the text of the alias. The characters /, $, `, and = and any of the shell\r\nhttps://linux.die.net/man/1/bash\r\nPage 36 of 107\n\nmetacharacters or quoting characters listed above may not appear in an alias name. The replacement text may\r\ncontain any valid shell input, including shell metacharacters. The first word of the replacement text is tested for\r\naliases, but a word that is identical to an alias being expanded is not expanded a second time. This means that one\r\nmay alias ls to ls -F, for instance, and bash does not try to recursively expand the replacement text. If the last\r\ncharacter of the alias value is a blank, then the next command word following the alias is also checked for alias\r\nexpansion.\r\nAliases are created and listed with the alias command, and removed with the unalias command.\r\nThere is no mechanism for using arguments in the replacement text. If arguments are needed, a shell function\r\nshould be used (see FUNCTIONS below).\r\nAliases are not expanded when the shell is not interactive, unless the expand_aliases shell option is set using\r\nshopt (see the description of shopt under SHELL BUILTIN COMMANDS below).\r\nThe rules concerning the definition and use of aliases are somewhat confusing. Bash always reads at least one\r\ncomplete line of input before executing any of the commands on that line. Aliases are expanded when a command\r\nis read, not when it is executed. Therefore, an alias definition appearing on the same line as another command\r\ndoes not take effect until the next line of input is read. The commands following the alias definition on that line\r\nare not affected by the new alias. This behavior is also an issue when functions are executed. Aliases are expanded\r\nwhen a function definition is read, not when the function is executed, because a function definition is itself a\r\ncompound command. As a consequence, aliases defined in a function are not available until after that function is\r\nexecuted. To be safe, always put alias definitions on a separate line, and do not use alias in compound commands.\r\nFor almost every purpose, aliases are superseded by shell functions.\r\nFunctions\r\nA shell function, defined as described above under SHELL GRAMMAR, stores a series of commands for later\r\nexecution. When the name of a shell function is used as a simple command name, the list of commands associated\r\nwith that function name is executed. Functions are executed in the context of the current shell; no new process is\r\ncreated to interpret them (contrast this with the execution of a shell script). When a function is executed, the\r\narguments to the function become the positional parameters during its execution. The special parameter # is\r\nupdated to reflect the change. Special parameter 0 is unchanged. The first element of the FUNCNAME variable is\r\nset to the name of the function while the function is executing.\r\nAll other aspects of the shell execution environment are identical between a function and its caller with these\r\nexceptions: the DEBUG and RETURN traps (see the description of the trap builtin under SHELL BUILTIN\r\nCOMMANDS below) are not inherited unless the function has been given the trace attribute (see the description of\r\nthe declare builtin below) or the -o functrace shell option has been enabled with the set builtin (in which case all\r\nfunctions inherit the DEBUG and RETURN traps), and the ERR trap is not inherited unless the -o errtrace shell\r\noption has been enabled.\r\nVariables local to the function may be declared with the local builtin command. Ordinarily, variables and their\r\nvalues are shared between the function and its caller.\r\nhttps://linux.die.net/man/1/bash\r\nPage 37 of 107\n\nIf the builtin command return is executed in a function, the function completes and execution resumes with the\r\nnext command after the function call. Any command associated with the RETURN trap is executed before\r\nexecution resumes. When a function completes, the values of the positional parameters and the special parameter\r\n# are restored to the values they had prior to the function's execution.\r\nFunction names and definitions may be listed with the -f option to the declare or typeset builtin commands. The -\r\nF option to declare or typeset will list the function names only (and optionally the source file and line number, if\r\nthe extdebug shell option is enabled). Functions may be exported so that subshells automatically have them\r\ndefined with the -f option to the export builtin. A function definition may be deleted using the -f option to the\r\nunset builtin. Note that shell functions and variables with the same name may result in multiple identically-named\r\nentries in the environment passed to the shell's children. Care should be taken in cases where this may cause a\r\nproblem.\r\nFunctions may be recursive. No limit is imposed on the number of recursive calls.\r\nArithmetic Evaluation\r\nThe shell allows arithmetic expressions to be evaluated, under certain circumstances (see the let and declare\r\nbuiltin commands and Arithmetic Expansion). Evaluation is done in fixed-width integers with no check for\r\noverflow, though division by 0 is trapped and flagged as an error. The operators and their precedence,\r\nassociativity, and values are the same as in the C language. The following list of operators is grouped into levels of\r\nequal-precedence operators. The levels are listed in order of decreasing precedence.\r\nid++ id--\r\nvariable post-increment and post-decrement\r\n++id --id\r\nvariable pre-increment and pre-decrement\r\n- +\r\nunary minus and plus\r\n! ~\r\nlogical and bitwise negation\r\n**\r\nexponentiation\r\n* / %\r\nmultiplication, division, remainder\r\n+ -\r\naddition, subtraction\r\nhttps://linux.die.net/man/1/bash\r\nPage 38 of 107\n\n\u003c\u003c \u003e\u003e\r\nleft and right bitwise shifts\r\n\u003c= \u003e= \u003c \u003e\r\ncomparison\r\n== !=\r\nequality and inequality\r\n\u0026\r\nbitwise AND\r\n^\r\nbitwise exclusive OR\r\n|\r\nbitwise OR\r\n\u0026\u0026\r\nlogical AND\r\n||\r\nlogical OR\r\nexpr?expr:expr\r\nconditional operator\r\n= *= /= %= += -= \u003c\u003c= \u003e\u003e= \u0026= ^= |=\r\nassignment\r\nexpr1 , expr2\r\ncomma\r\nShell variables are allowed as operands; parameter expansion is performed before the expression is evaluated.\r\nWithin an expression, shell variables may also be referenced by name without using the parameter expansion\r\nsyntax. A shell variable that is null or unset evaluates to 0 when referenced by name without using the parameter\r\nexpansion syntax. The value of a variable is evaluated as an arithmetic expression when it is referenced, or when a\r\nvariable which has been given the integer attribute using declare -i is assigned a value. A null value evaluates to 0.\r\nA shell variable need not have its integer attribute turned on to be used in an expression.\r\nConstants with a leading 0 are interpreted as octal numbers. A leading 0x or 0X denotes hexadecimal. Otherwise,\r\nnumbers take the form [base#]n, where base is a decimal number between 2 and 64 representing the arithmetic\r\nbase, and n is a number in that base. If base# is omitted, then base 10 is used. The digits greater than 9 are\r\nrepresented by the lowercase letters, the uppercase letters, @, and _, in that order. If base is less than or equal to\r\n36, lowercase and uppercase letters may be used interchangeably to represent numbers between 10 and 35.\r\nhttps://linux.die.net/man/1/bash\r\nPage 39 of 107\n\nOperators are evaluated in order of precedence. Sub-expressions in parentheses are evaluated first and may\r\noverride the precedence rules above.\r\nConditional Expressions\r\nConditional expressions are used by the [[ compound command and the test and [ builtin commands to test file\r\nattributes and perform string and arithmetic comparisons. Expressions are formed from the following unary or\r\nbinary primaries. If any file argument to one of the primaries is of the form /dev/fd/n, then file descriptor n is\r\nchecked. If the file argument to one of the primaries is one of /dev/stdin, /dev/stdout, or /dev/stderr, file descriptor\r\n0, 1, or 2, respectively, is checked.\r\nUnless otherwise specified, primaries that operate on files follow symbolic links and operate on the target of the\r\nlink, rather than the link itself.\r\nWhen used with [[, The \u003c and \u003e operators sort lexicographically using the current locale.\r\n-a file\r\nTrue if file exists.\r\n-b file\r\nTrue if file exists and is a block special file.\r\n-c file\r\nTrue if file exists and is a character special file.\r\n-d file\r\nTrue if file exists and is a directory.\r\n-e file\r\nTrue if file exists.\r\n-f file\r\nTrue if file exists and is a regular file.\r\n-g file\r\nTrue if file exists and is set-group-id.\r\n-h file\r\nTrue if file exists and is a symbolic link.\r\n-k file\r\nTrue if file exists and its ''sticky'' bit is set.\r\n-p file\r\nTrue if file exists and is a named pipe (FIFO).\r\n-r file\r\nTrue if file exists and is readable.\r\n-s file\r\nTrue if file exists and has a size greater than zero.\r\n-t fd\r\nTrue if file descriptor fd is open and refers to a terminal.\r\nhttps://linux.die.net/man/1/bash\r\nPage 40 of 107\n\n-u file\r\nTrue if file exists and its set-user-id bit is set.\r\n-w file\r\nTrue if file exists and is writable.\r\n-x file\r\nTrue if file exists and is executable.\r\n-O file\r\nTrue if file exists and is owned by the effective user id.\r\n-G file\r\nTrue if file exists and is owned by the effective group id.\r\n-L file\r\nTrue if file exists and is a symbolic link.\r\n-S file\r\nTrue if file exists and is a socket.\r\n-N file\r\nTrue if file exists and has been modified since it was last read.\r\nfile1 -nt file2\r\nTrue if file1 is newer (according to modification date) than file2, or if file1 exists and file2 does not.\r\nfile1 -ot file2\r\nTrue if file1 is older than file2, or if file2 exists and file1 does not.\r\nfile1 -ef file2\r\nTrue if file1 and file2 refer to the same device and inode numbers.\r\n-o optname\r\nTrue if shell option optname is enabled. See the list of options under the description of the -o option to the\r\nset builtin below.\r\n-z string\r\nTrue if the length of string is zero.\r\nstring\r\n-n string\r\nTrue if the length of string is non-zero.\r\nstring1 == string2\r\nstring1 = string2\r\nTrue if the strings are equal. = should be used with the test command for POSIX conformance.\r\nstring1 != string2\r\nTrue if the strings are not equal.\r\nstring1 \u003c string2\r\nTrue if string1 sorts before string2 lexicographically.\r\nstring1 \u003e string2\r\nTrue if string1 sorts after string2 lexicographically.\r\narg1 OP arg2\r\nOP is one of -eq, -ne, -lt, -le, -gt, or -ge. These arithmetic binary operators return true if arg1 is equal to,\r\nnot equal to, less than, less than or equal to, greater than, or greater than or equal to arg2, respectively.\r\nhttps://linux.die.net/man/1/bash\r\nPage 41 of 107\n\nArg1 and arg2 may be positive or negative integers.\r\nSimple Command Expansion\r\nWhen a simple command is executed, the shell performs the following expansions, assignments, and redirections,\r\nfrom left to right.\r\n1.\r\nThe words that the parser has marked as variable assignments (those preceding the command name) and\r\nredirections are saved for later processing.\r\n2.\r\nThe words that are not variable assignments or redirections are expanded. If any words remain after expansion, the\r\nfirst word is taken to be the name of the command and the remaining words are the arguments.\r\n3.\r\nRedirections are performed as described above under REDIRECTION.\r\n4.\r\nThe text after the = in each variable assignment undergoes tilde expansion, parameter expansion, command\r\nsubstitution, arithmetic expansion, and quote removal before being assigned to the variable.\r\nIf no command name results, the variable assignments affect the current shell environment. Otherwise, the\r\nvariables are added to the environment of the executed command and do not affect the current shell environment.\r\nIf any of the assignments attempts to assign a value to a readonly variable, an error occurs, and the command exits\r\nwith a non-zero status.\r\nIf no command name results, redirections are performed, but do not affect the current shell environment. A\r\nredirection error causes the command to exit with a non-zero status.\r\nIf there is a command name left after expansion, execution proceeds as described below. Otherwise, the command\r\nexits. If one of the expansions contained a command substitution, the exit status of the command is the exit status\r\nof the last command substitution performed. If there were no command substitutions, the command exits with a\r\nstatus of zero.\r\nCommand Execution\r\nAfter a command has been split into words, if it results in a simple command and an optional list of arguments, the\r\nfollowing actions are taken.\r\nIf the command name contains no slashes, the shell attempts to locate it. If there exists a shell function by that\r\nname, that function is invoked as described above in FUNCTIONS. If the name does not match a function, the shell\r\nsearches for it in the list of shell builtins. If a match is found, that builtin is invoked.\r\nhttps://linux.die.net/man/1/bash\r\nPage 42 of 107\n\nIf the name is neither a shell function nor a builtin, and contains no slashes, bash searches each element of the\r\nPATH for a directory containing an executable file by that name. Bash uses a hash table to remember the full\r\npathnames of executable files (see hash under SHELL BUILTIN COMMANDS below). A full search of the\r\ndirectories in PATH is performed only if the command is not found in the hash table. If the search is unsuccessful,\r\nthe shell searches for a defined shell function named command_not_found_handle. If that function exists, it is\r\ninvoked with the original command and the original command's arguments as its arguments, and the function's\r\nexit status becomes the exit status of the shell. If that function is not defined, the shell prints an error message and\r\nreturns an exit status of 127.\r\nIf the search is successful, or if the command name contains one or more slashes, the shell executes the named\r\nprogram in a separate execution environment. Argument 0 is set to the name given, and the remaining arguments\r\nto the command are set to the arguments given, if any.\r\nIf this execution fails because the file is not in executable format, and the file is not a directory, it is assumed to be\r\na shell script, a file containing shell commands. A subshell is spawned to execute it. This subshell reinitializes\r\nitself, so that the effect is as if a new shell had been invoked to handle the script, with the exception that the\r\nlocations of commands remembered by the parent (see hash below under SHELL BUILTIN COMMANDS) are\r\nretained by the child.\r\nIf the program is a file beginning with #!, the remainder of the first line specifies an interpreter for the program.\r\nThe shell executes the specified interpreter on operating systems that do not handle this executable format\r\nthemselves. The arguments to the interpreter consist of a single optional argument following the interpreter name\r\non the first line of the program, followed by the name of the program, followed by the command arguments, if\r\nany.\r\nCommand Execution Environment\r\nThe shell has an execution environment, which consists of the following:\r\n• open files inherited by the shell at invocation, as modified by redirections supplied to the exec builtin\r\n• the current working directory as set by cd, pushd, or popd, or inherited by the shell at invocation\r\n• the file creation mode mask as set by umask or inherited from the shell's parent\r\n• current traps set by trap\r\n• shell parameters that are set by variable assignment or with set or inherited from the shell's parent in the\r\nenvironment\r\n• shell functions defined during execution or inherited from the shell's parent in the environment\r\n• options enabled at invocation (either by default or with command-line arguments) or by set\r\n• options enabled by shopt\r\n• shell aliases defined with alias\r\nhttps://linux.die.net/man/1/bash\r\nPage 43 of 107\n\n• various process IDs, including those of background jobs, the value of $$, and the value of PPID\r\nWhen a simple command other than a builtin or shell function is to be executed, it is invoked in a separate\r\nexecution environment that consists of the following. Unless otherwise noted, the values are inherited from the\r\nshell.\r\n• the shell's open files, plus any modifications and additions specified by redirections to the command\r\n• the current working directory\r\n• the file creation mode mask\r\n• shell variables and functions marked for export, along with variables exported for the command, passed in the\r\nenvironment\r\n• traps caught by the shell are reset to the values inherited from the shell's parent, and traps ignored by the shell\r\nare ignored\r\nA command invoked in this separate environment cannot affect the shell's execution environment.\r\nCommand substitution, commands grouped with parentheses, and asynchronous commands are invoked in a\r\nsubshell environment that is a duplicate of the shell environment, except that traps caught by the shell are reset to\r\nthe values that the shell inherited from its parent at invocation. Builtin commands that are invoked as part of a\r\npipeline are also executed in a subshell environment. Changes made to the subshell environment cannot affect the\r\nshell's execution environment.\r\nSubshells spawned to execute command substitutions inherit the value of the -e option from the parent shell.\r\nWhen not in posix mode, Bash clears the -e option in such subshells.\r\nIf a command is followed by a \u0026 and job control is not active, the default standard input for the command is the\r\nempty file /dev/null. Otherwise, the invoked command inherits the file descriptors of the calling shell as modified\r\nby redirections.\r\nEnvironment\r\nWhen a program is invoked it is given an array of strings called the environment. This is a list of name-value pairs,\r\nof the form name=value.\r\nThe shell provides several ways to manipulate the environment. On invocation, the shell scans its own\r\nenvironment and creates a parameter for each name found, automatically marking it for export to child processes.\r\nExecuted commands inherit the environment. The export and declare -x commands allow parameters and\r\nfunctions to be added to and deleted from the environment. If the value of a parameter in the environment is\r\nmodified, the new value becomes part of the environment, replacing the old. The environment inherited by any\r\nexecuted command consists of the shell's initial environment, whose values may be modified in the shell, less any\r\npairs removed by the unset command, plus any additions via the export and declare -x commands.\r\nThe environment for any simple command or function may be augmented temporarily by prefixing it with\r\nparameter assignments, as described above in PARAMETERS. These assignment statements affect only the\r\nhttps://linux.die.net/man/1/bash\r\nPage 44 of 107\n\nenvironment seen by that command.\r\nIf the -k option is set (see the set builtin command below), then all parameter assignments are placed in the\r\nenvironment for a command, not just those that precede the command name.\r\nWhen bash invokes an external command, the variable _ is set to the full file name of the command and passed to\r\nthat command in its environment.\r\nExit Status\r\nThe exit status of an executed command is the value returned by the waitpid system call or equivalent function.\r\nExit statuses fall between 0 and 255, though, as explained below, the shell may use values above 125 specially.\r\nExit statuses from shell builtins and compound commands are also limited to this range. Under certain\r\ncircumstances, the shell will use special values to indicate specific failure modes.\r\nFor the shell's purposes, a command which exits with a zero exit status has succeeded. An exit status of zero\r\nindicates success. A non-zero exit status indicates failure. When a command terminates on a fatal signal N, bash\r\nuses the value of 128+N as the exit status.\r\nIf a command is not found, the child process created to execute it returns a status of 127. If a command is found\r\nbut is not executable, the return status is 126.\r\nIf a command fails because of an error during expansion or redirection, the exit status is greater than zero.\r\nShell builtin commands return a status of 0 (true) if successful, and non-zero (false) if an error occurs while they\r\nexecute. All builtins return an exit status of 2 to indicate incorrect usage.\r\nBash itself returns the exit status of the last command executed, unless a syntax error occurs, in which case it exits\r\nwith a non-zero value. See also the exit builtin command below.\r\nSignals\r\nWhen bash is interactive, in the absence of any traps, it ignores SIGTERM (so that kill 0 does not kill an\r\ninteractive shell), and SIGINT is caught and handled (so that the wait builtin is interruptible). In all cases, bash\r\nignores SIGQUIT. If job control is in effect, bash ignores SIGTTIN, SIGTTOU, and SIGTSTP.\r\nNon-builtin commands run by bash have signal handlers set to the values inherited by the shell from its parent.\r\nWhen job control is not in effect, asynchronous commands ignore SIGINT and SIGQUIT in addition to these\r\ninherited handlers. Commands run as a result of command substitution ignore the keyboard-generated job control\r\nsignals SIGTTIN, SIGTTOU, and SIGTSTP.\r\nThe shell exits by default upon receipt of a SIGHUP. Before exiting, an interactive shell resends the SIGHUP to all\r\njobs, running or stopped. Stopped jobs are sent SIGCONT to ensure that they receive the SIGHUP. To prevent the\r\nshell from sending the signal to a particular job, it should be removed from the jobs table with the disown builtin\r\n(see SHELL BUILTIN COMMANDS below) or marked to not receive SIGHUP using disown -h.\r\nhttps://linux.die.net/man/1/bash\r\nPage 45 of 107\n\nIf the huponexit shell option has been set with shopt, bash sends a SIGHUP to all jobs when an interactive login\r\nshell exits.\r\nIf bash is waiting for a command to complete and receives a signal for which a trap has been set, the trap will not\r\nbe executed until the command completes. When bash is waiting for an asynchronous command via the wait\r\nbuiltin, the reception of a signal for which a trap has been set will cause the wait builtin to return immediately\r\nwith an exit status greater than 128, immediately after which the trap is executed.\r\nJob Control\r\nJob control refers to the ability to selectively stop (suspend) the execution of processes and continue (resume)\r\ntheir execution at a later point. A user typically employs this facility via an interactive interface supplied jointly by\r\nthe operating system kernel's terminal driver and bash.\r\nThe shell associates a job with each pipeline. It keeps a table of currently executing jobs, which may be listed with\r\nthe jobs command. When bash starts a job asynchronously (in the background), it prints a line that looks like:\r\n[1] 25647\r\nindicating that this job is job number 1 and that the process ID of the last process in the pipeline associated with\r\nthis job is 25647. All of the processes in a single pipeline are members of the same job. Bash uses the job\r\nabstraction as the basis for job control.\r\nTo facilitate the implementation of the user interface to job control, the operating system maintains the notion of a\r\ncurrent terminal process group ID. Members of this process group (processes whose process group ID is equal to\r\nthe current terminal process group ID) receive keyboard-generated signals such as SIGINT. These processes are\r\nsaid to be in the foreground. Background processes are those whose process group ID differs from the terminal's;\r\nsuch processes are immune to keyboard-generated signals. Only foreground processes are allowed to read from or,\r\nif the user so specifies with stty tostop, write to the terminal. Background processes which attempt to read from\r\n(write to when stty tostop is in effect) the terminal are sent a SIGTTIN (SIGTTOU) signal by the kernel's\r\nterminal driver, which, unless caught, suspends the process.\r\nIf the operating system on which bash is running supports job control, bash contains facilities to use it. Typing the\r\nsuspend character (typically ^Z, Control-Z) while a process is running causes that process to be stopped and\r\nreturns control to bash. Typing the delayed suspend character (typically ^Y, Control-Y) causes the process to be\r\nstopped when it attempts to read input from the terminal, and control to be returned to bash. The user may then\r\nmanipulate the state of this job, using the bg command to continue it in the background, the fg command to\r\ncontinue it in the foreground, or the kill command to kill it. A ^Z takes effect immediately, and has the additional\r\nside effect of causing pending output and typeahead to be discarded.\r\nThere are a number of ways to refer to a job in the shell. The character % introduces a job specification (jobspec).\r\nJob number n may be referred to as %n. A job may also be referred to using a prefix of the name used to start it,\r\nor using a substring that appears in its command line. For example, %ce refers to a stopped ce job. If a prefix\r\nmatches more than one job, bash reports an error. Using %?ce, on the other hand, refers to any job containing the\r\nstring ce in its command line. If the substring matches more than one job, bash reports an error. The symbols %%\r\nand %+ refer to the shell's notion of the current job, which is the last job stopped while it was in the foreground or\r\nhttps://linux.die.net/man/1/bash\r\nPage 46 of 107\n\nstarted in the background. The previous job may be referenced using %-. If there is only a single job, %+ and %-\r\ncan both be used to refer to that job. In output pertaining to jobs (e.g., the output of the jobs command), the\r\ncurrent job is always flagged with a +, and the previous job with a -. A single % (with no accompanying job\r\nspecification) also refers to the current job.\r\nSimply naming a job can be used to bring it into the foreground: %1 is a synonym for ''fg %1'', bringing job 1\r\nfrom the background into the foreground. Similarly, ''%1 \u0026'' resumes job 1 in the background, equivalent to ''bg\r\n%1''.\r\nThe shell learns immediately whenever a job changes state. Normally, bash waits until it is about to print a prompt\r\nbefore reporting changes in a job's status so as to not interrupt any other output. If the -b option to the set builtin\r\ncommand is enabled, bash reports such changes immediately. Any trap on SIGCHLD is executed for each child\r\nthat exits.\r\nIf an attempt to exit bash is made while jobs are stopped (or, if the checkjobs shell option has been enabled using\r\nthe shopt builtin, running), the shell prints a warning message, and, if the checkjobs option is enabled, lists the\r\njobs and their statuses. The jobs command may then be used to inspect their status. If a second attempt to exit is\r\nmade without an intervening command, the shell does not print another warning, and any stopped jobs are\r\nterminated.\r\nPrompting\r\nWhen executing interactively, bash displays the primary prompt PS1 when it is ready to read a command, and the\r\nsecondary prompt PS2 when it needs more input to complete a command. Bash allows these prompt strings to be\r\ncustomized by inserting a number of backslash-escaped special characters that are decoded as follows:\r\n\\a\r\nan ASCII bell character (07)\r\n\\d\r\nthe date in \"Weekday Month Date\" format (e.g., \"Tue May 26\")\r\n\\D{format}\r\nthe format is passed to strftime(3) and the result is inserted into the prompt string; an empty format results in a\r\nlocale-specific time representation. The braces are required\r\n\\e\r\nan ASCII escape character (033)\r\n\\h\r\nthe hostname up to the first '.'\r\n\\H\r\nhttps://linux.die.net/man/1/bash\r\nPage 47 of 107\n\nthe hostname\r\n\\j\r\nthe number of jobs currently managed by the shell\r\n\\l\r\nthe basename of the shell's terminal device name\r\n\\n\r\nnewline\r\n\\r\r\ncarriage return\r\n\\s\r\nthe name of the shell, the basename of $0 (the portion following the final slash)\r\n\\t\r\nthe current time in 24-hour HH:MM:SS format\r\n\\T\r\nthe current time in 12-hour HH:MM:SS format\r\n\\@\r\nthe current time in 12-hour am/pm format\r\n\\A\r\nthe current time in 24-hour HH:MM format\r\n\\u\r\nthe username of the current user\r\n\\v\r\nthe version of bash (e.g., 2.00)\r\n\\V\r\nthe release of bash, version + patch level (e.g., 2.00.0)\r\n\\w\r\nhttps://linux.die.net/man/1/bash\r\nPage 48 of 107\n\nthe current working directory, with $HOME abbreviated with a tilde (uses the value of the\r\nPROMPT_DIRTRIM variable)\r\n\\W\r\nthe basename of the current working directory, with $HOME abbreviated with a tilde\r\n\\!\r\nthe history number of this command\r\n\\#\r\nthe command number of this command\r\n\\$\r\nif the effective UID is 0, a #, otherwise a $\r\n\\nnn\r\nthe character corresponding to the octal number nnn\r\n\\\\\r\na backslash\r\n\\[\r\nbegin a sequence of non-printing characters, which could be used to embed a terminal control sequence\r\ninto the prompt\r\n\\]\r\nend a sequence of non-printing characters\r\nThe command number and the history number are usually different: the history number of a command is its\r\nposition in the history list, which may include commands restored from the history file (see HISTORY below),\r\nwhile the command number is the position in the sequence of commands executed during the current shell session.\r\nAfter the string is decoded, it is expanded via parameter expansion, command substitution, arithmetic expansion,\r\nand quote removal, subject to the value of the promptvars shell option (see the description of the shopt command\r\nunder SHELL BUILTIN COMMANDS below).\r\nReadline\r\nThis is the library that handles reading input when using an interactive shell, unless the --noediting option is given\r\nat shell invocation. Line editing is also used when using the -e option to the read builtin. By default, the line\r\nediting commands are similar to those of emacs. A vi-style line editing interface is also available. Line editing can\r\nhttps://linux.die.net/man/1/bash\r\nPage 49 of 107\n\nbe enabled at any time using the -o emacs or -o vi options to the set builtin (see SHELL BUILTIN COMMANDS\r\nbelow). To turn off line editing after the shell is running, use the +o emacs or +o vi options to the set builtin.\r\nReadline Notation\r\nIn this section, the emacs-style notation is used to denote keystrokes. Control keys are denoted by C-key, e.g., C-n\r\nmeans Control-N. Similarly, meta keys are denoted by M-key, so M-x means Meta-X. (On keyboards without a\r\nmeta key, M-x means ESC x, i.e., press the Escape key then the x key. This makes ESC the meta prefix. The\r\ncombination M-C-x means ESC-Control-x, or press the Escape key then hold the Control key while pressing the x\r\nkey.)\r\nReadline commands may be given numeric arguments, which normally act as a repeat count. Sometimes,\r\nhowever, it is the sign of the argument that is significant. Passing a negative argument to a command that acts in\r\nthe forward direction (e.g., kill-line) causes that command to act in a backward direction. Commands whose\r\nbehavior with arguments deviates from this are noted below.\r\nWhen a command is described as killing text, the text deleted is saved for possible future retrieval (yanking). The\r\nkilled text is saved in a kill ring. Consecutive kills cause the text to be accumulated into one unit, which can be\r\nyanked all at once. Commands which do not kill text separate the chunks of text on the kill ring.\r\nReadline Initialization\r\nReadline is customized by putting commands in an initialization file (the inputrc file). The name of this file is\r\ntaken from the value of the INPUTRC variable. If that variable is unset, the default is ~/.inputrc. When a program\r\nwhich uses the readline library starts up, the initialization file is read, and the key bindings and variables are set.\r\nThere are only a few basic constructs allowed in the readline initialization file. Blank lines are ignored. Lines\r\nbeginning with a # are comments. Lines beginning with a $ indicate conditional constructs. Other lines denote key\r\nbindings and variable settings.\r\nThe default key-bindings may be changed with an inputrc file. Other programs that use this library may add their\r\nown commands and bindings.\r\nFor example, placing\r\nM-Control-u: universal-argument\r\nor\r\nC-Meta-u: universal-argument\r\ninto the inputrc would make M-C-u execute the readline command universal-argument.\r\nThe following symbolic character names are recognized: RUBOUT, DEL, ESC, LFD, NEWLINE, RET, RETURN,\r\nSPC, SPACE, and TAB.\r\nIn addition to command names, readline allows keys to be bound to a string that is inserted when the key is\r\npressed (a macro).\r\nReadline Key Bindings\r\nhttps://linux.die.net/man/1/bash\r\nPage 50 of 107\n\nThe syntax for controlling key bindings in the inputrc file is simple. All that is required is the name of the\r\ncommand or the text of a macro and a key sequence to which it should be bound. The name may be specified in\r\none of two ways: as a symbolic key name, possibly with Meta- or Control- prefixes, or as a key sequence.\r\nWhen using the form keyname:function-name or macro, keyname is the name of a key spelled out in English. For\r\nexample:\r\nControl-u: universal-argument\r\nMeta-Rubout: backward-kill-word\r\nControl-o: \"\u003e output\"\r\nIn the above example, C-u is bound to the function universal-argument, M-DEL is bound to the function\r\nbackward-kill-word, and C-o is bound to run the macro expressed on the right hand side (that is, to insert the text\r\n''\u003e output'' into the line).\r\nIn the second form, \"keyseq\":function-name or macro, keyseq differs from keyname above in that strings\r\ndenoting an entire key sequence may be specified by placing the sequence within double quotes. Some GNU\r\nEmacs style key escapes can be used, as in the following example, but the symbolic character names are not\r\nrecognized.\r\n\"\\C-u\": universal-argument\r\n\"\\C-x\\C-r\": re-read-init-file\r\n\"\\e[11~\": \"Function Key 1\"\r\nIn this example, C-u is again bound to the function universal-argument. C-x C-r is bound to the function re-read-init-file, and ESC [ 1 1 ~ is bound to insert the text ''Function Key 1''.\r\nThe full set of GNU Emacs style escape sequences is\r\n\\C-control prefix\r\n\\M-meta prefix\r\n\\e\r\nan escape character\r\n\\\\\r\nbackslash\r\n\\\"\r\nliteral \"\r\n\\'\r\nhttps://linux.die.net/man/1/bash\r\nPage 51 of 107\n\nliteral '\r\nIn addition to the GNU Emacs style escape sequences, a second set of backslash escapes is available:\r\n\\a\r\nalert (bell)\r\n\\b\r\nbackspace\r\n\\d\r\ndelete\r\n\\f\r\nform feed\r\n\\n\r\nnewline\r\n\\r\r\ncarriage return\r\n\\t\r\nhorizontal tab\r\n\\v\r\nvertical tab\r\n\\nnn\r\nthe eight-bit character whose value is the octal value nnn (one to three digits)\r\n\\xHH\r\nthe eight-bit character whose value is the hexadecimal value HH (one or two hex digits)\r\nWhen entering the text of a macro, single or double quotes must be used to indicate a macro definition. Unquoted\r\ntext is assumed to be a function name. In the macro body, the backslash escapes described above are expanded.\r\nBackslash will quote any other character in the macro text, including \" and '.\r\nBash allows the current readline key bindings to be displayed or modified with the bind builtin command. The\r\nediting mode may be switched during interactive use by using the -o option to the set builtin command (see\r\nSHELL BUILTIN COMMANDS below).\r\nhttps://linux.die.net/man/1/bash\r\nPage 52 of 107\n\nReadline Variables\r\nReadline has variables that can be used to further customize its behavior. A variable may be set in the inputrc file\r\nwith a statement of the form\r\nset variable-name value\r\nExcept where noted, readline variables can take the values On or Off (without regard to case). Unrecognized\r\nvariable names are ignored. When a variable value is read, empty or null values, \"on\" (case-insensitive), and \"1\"\r\nare equivalent to On. All other values are equivalent to Off. The variables and their default values are:\r\nbell-style (audible)\r\nControls what happens when readline wants to ring the terminal bell. If set to none, readline never rings\r\nthe bell. If set to visible, readline uses a visible bell if one is available. If set to audible, readline attempts\r\nto ring the terminal's bell.\r\nbind-tty-special-chars (On)\r\nIf set to On, readline attempts to bind the control characters treated specially by the kernel's terminal driver\r\nto their readline equivalents.\r\ncomment-begin (''#'')\r\nThe string that is inserted when the readline insert-comment command is executed. This command is\r\nbound to M-# in emacs mode and to # in vi command mode.\r\ncompletion-ignore-case (Off)\r\nIf set to On, readline performs filename matching and completion in a case-insensitive fashion.\r\ncompletion-prefix-display-length (0)\r\nThe length in characters of the common prefix of a list of possible completions that is displayed without\r\nmodification. When set to a value greater than zero, common prefixes longer than this value are replaced\r\nwith an ellipsis when displaying possible completions.\r\ncompletion-query-items (100)\r\nThis determines when the user is queried about viewing the number of possible completions generated by\r\nthe possible-completions command. It may be set to any integer value greater than or equal to zero. If the\r\nnumber of possible completions is greater than or equal to the value of this variable, the user is asked\r\nwhether or not he wishes to view them; otherwise they are simply listed on the terminal.\r\nconvert-meta (On)\r\nIf set to On, readline will convert characters with the eighth bit set to an ASCII key sequence by stripping\r\nthe eighth bit and prefixing an escape character (in effect, using escape as the meta prefix).\r\ndisable-completion (Off)\r\nIf set to On, readline will inhibit word completion. Completion characters will be inserted into the line as if\r\nthey had been mapped to self-insert.\r\nediting-mode (emacs)\r\nControls whether readline begins with a set of key bindings similar to emacs or vi. editing-mode can be set\r\nto either emacs or vi.\r\necho-control-characters (On)\r\nWhen set to On, on operating systems that indicate they support it, readline echoes a character\r\ncorresponding to a signal generated from the keyboard.\r\nenable-keypad (Off)\r\nhttps://linux.die.net/man/1/bash\r\nPage 53 of 107\n\nWhen set to On, readline will try to enable the application keypad when it is called. Some systems need\r\nthis to enable the arrow keys.\r\nenable-meta-key (On)\r\nWhen set to On, readline will try to enable any meta modifier key the terminal claims to support when it is\r\ncalled. On many terminals, the meta key is used to send eight-bit characters.\r\nexpand-tilde (Off)\r\nIf set to on, tilde expansion is performed when readline attempts word completion.\r\nhistory-preserve-point (Off)\r\nIf set to on, the history code attempts to place point at the same location on each history line retrieved with\r\nprevious-history or next-history.\r\nhistory-size (0)\r\nSet the maximum number of history entries saved in the history list. If set to zero, the number of entries in\r\nthe history list is not limited.\r\nhorizontal-scroll-mode (Off)\r\nWhen set to On, makes readline use a single line for display, scrolling the input horizontally on a single\r\nscreen line when it becomes longer than the screen width rather than wrapping to a new line.\r\ninput-meta (Off)\r\nIf set to On, readline will enable eight-bit input (that is, it will not strip the high bit from the characters it\r\nreads), regardless of what the terminal claims it can support. The name meta-flag is a synonym for this\r\nvariable.\r\nisearch-terminators (''C-[C-J'')\r\nThe string of characters that should terminate an incremental search without subsequently executing the\r\ncharacter as a command. If this variable has not been given a value, the characters ESC and C-J will\r\nterminate an incremental search.\r\nkeymap (emacs)\r\nSet the current readline keymap. The set of valid keymap names is emacs, emacs-standard, emacs-meta,\r\nemacs-ctlx, vi, vi-command, and vi-insert. vi is equivalent to vi-command; emacs is equivalent to emacs-standard. The default value is emacs; the value of editing-mode also affects the default keymap.\r\nmark-directories (On)\r\nIf set to On, completed directory names have a slash appended.\r\nmark-modified-lines (Off)\r\nIf set to On, history lines that have been modified are displayed with a preceding asterisk (*).\r\nmark-symlinked-directories (Off)\r\nIf set to On, completed names which are symbolic links to directories have a slash appended (subject to the\r\nvalue of mark-directories).\r\nmatch-hidden-files (On)\r\nThis variable, when set to On, causes readline to match files whose names begin with a '.' (hidden files)\r\nwhen performing filename completion, unless the leading '.' is supplied by the user in the filename to be\r\ncompleted.\r\noutput-meta (Off)\r\nIf set to On, readline will display characters with the eighth bit set directly rather than as a meta-prefixed\r\nescape sequence.\r\nhttps://linux.die.net/man/1/bash\r\nPage 54 of 107\n\npage-completions (On)\r\nIf set to On, readline uses an internal more-like pager to display a screenful of possible completions at a\r\ntime.\r\nprint-completions-horizontally (Off)\r\nIf set to On, readline will display completions with matches sorted horizontally in alphabetical order, rather\r\nthan down the screen.\r\nrevert-all-at-newline (Off)\r\nIf set to on, readline will undo all changes to history lines before returning when accept-line is executed.\r\nBy default, history lines may be modified and retain individual undo lists across calls to readline.\r\nshow-all-if-ambiguous (Off)\r\nThis alters the default behavior of the completion functions. If set to on, words which have more than one\r\npossible completion cause the matches to be listed immediately instead of ringing the bell.\r\nshow-all-if-unmodified (Off)\r\nThis alters the default behavior of the completion functions in a fashion similar to show-all-if-ambiguous.\r\nIf set to on, words which have more than one possible completion without any possible partial completion\r\n(the possible completions don't share a common prefix) cause the matches to be listed immediately instead\r\nof ringing the bell.\r\nskip-completed-text (Off)\r\nIf set to On, this alters the default completion behavior when inserting a single match into the line. It's only\r\nactive when performing completion in the middle of a word. If enabled, readline does not insert characters\r\nfrom the completion that match characters after point in the word being completed, so portions of the word\r\nfollowing the cursor are not duplicated.\r\nvisible-stats (Off)\r\nIf set to On, a character denoting a file's type as reported by stat(2) is appended to the filename when\r\nlisting possible completions.\r\nReadline Conditional Constructs\r\nReadline implements a facility similar in spirit to the conditional compilation features of the C preprocessor which\r\nallows key bindings and variable settings to be performed as the result of tests. There are four parser directives\r\nused.\r\n$if\r\nThe $if construct allows bindings to be made based on the editing mode, the terminal being used, or the\r\napplication using readline. The text of the test extends to the end of the line; no characters are required to isolate\r\nit.\r\nmode\r\nThe mode= form of the $if directive is used to test whether readline is in emacs or vi mode. This may be\r\nused in conjunction with the set keymap command, for instance, to set bindings in the emacs-standard and\r\nemacs-ctlx keymaps only if readline is starting out in emacs mode.\r\nterm\r\nhttps://linux.die.net/man/1/bash\r\nPage 55 of 107\n\nThe term= form may be used to include terminal-specific key bindings, perhaps to bind the key sequences\r\noutput by the terminal's function keys. The word on the right side of the = is tested against the both full\r\nname of the terminal and the portion of the terminal name before the first -. This allows sun to match both\r\nsun and sun-cmd, for instance.\r\napplication\r\nThe application construct is used to include application-specific settings. Each program using the readline library\r\nsets the application name, and an initialization file can test for a particular value. This could be used to bind key\r\nsequences to functions useful for a specific program. For instance, the following command adds a key sequence\r\nthat quotes the current or previous word in Bash:\r\n$if Bash\r\n# Quote the current or previous word\r\n\"\\C-xq\": \"\\eb\\\"\\ef\\\"\"\r\n$endif\r\n$endif\r\nThis command, as seen in the previous example, terminates an $if command.\r\n$else\r\nCommands in this branch of the $if directive are executed if the test fails.\r\n$include\r\nThis directive takes a single filename as an argument and reads commands and bindings from that file. For\r\nexample, the following directive would read /etc/inputrc:\r\n$include /etc/inputrc\r\nSearching\r\nReadline provides commands for searching through the command history (see HISTORY below) for lines\r\ncontaining a specified string. There are two search modes: incremental and non-incremental.\r\nIncremental searches begin before the user has finished typing the search string. As each character of the search\r\nstring is typed, readline displays the next entry from the history matching the string typed so far. An incremental\r\nsearch requires only as many characters as needed to find the desired history entry. The characters present in the\r\nvalue of the isearch-terminators variable are used to terminate an incremental search. If that variable has not\r\nbeen assigned a value the Escape and Control-J characters will terminate an incremental search. Control-G will\r\nabort an incremental search and restore the original line. When the search is terminated, the history entry\r\ncontaining the search string becomes the current line.\r\nTo find other matching entries in the history list, type Control-S or Control-R as appropriate. This will search\r\nbackward or forward in the history for the next entry matching the search string typed so far. Any other key\r\nhttps://linux.die.net/man/1/bash\r\nPage 56 of 107\n\nsequence bound to a readline command will terminate the search and execute that command. For instance, a\r\nnewline will terminate the search and accept the line, thereby executing the command from the history list.\r\nReadline remembers the last incremental search string. If two Control-Rs are typed without any intervening\r\ncharacters defining a new search string, any remembered search string is used.\r\nNon-incremental searches read the entire search string before starting to search for matching history lines. The\r\nsearch string may be typed by the user or be part of the contents of the current line.\r\nReadline Command Names\r\nThe following is a list of the names of the commands and the default key sequences to which they are bound.\r\nCommand names without an accompanying key sequence are unbound by default. In the following descriptions,\r\npoint refers to the current cursor position, and mark refers to a cursor position saved by the set-mark command.\r\nThe text between the point and mark is referred to as the region.\r\nCommands for Moving\r\nbeginning-of-line (C-a)\r\nMove to the start of the current line.\r\nend-of-line (C-e)\r\nMove to the end of the line.\r\nforward-char (C-f)\r\nMove forward a character.\r\nbackward-char (C-b)\r\nMove back a character.\r\nforward-word (M-f)\r\nMove forward to the end of the next word. Words are composed of alphanumeric characters (letters and\r\ndigits).\r\nbackward-word (M-b)\r\nMove back to the start of the current or previous word. Words are composed of alphanumeric characters\r\n(letters and digits).\r\nshell-forward-word\r\nMove forward to the end of the next word. Words are delimited by non-quoted shell metacharacters.\r\nshell-backward-word\r\nMove back to the start of the current or previous word. Words are delimited by non-quoted shell\r\nmetacharacters.\r\nclear-screen (C-l)\r\nClear the screen leaving the current line at the top of the screen. With an argument, refresh the current line\r\nwithout clearing the screen.\r\nredraw-current-line\r\nRefresh the current line.\r\nCommands for Manipulating the History\r\nhttps://linux.die.net/man/1/bash\r\nPage 57 of 107\n\naccept-line (Newline, Return)\r\nAccept the line regardless of where the cursor is. If this line is non-empty, add it to the history list\r\naccording to the state of the HISTCONTROL variable. If the line is a modified history line, then restore the\r\nhistory line to its original state.\r\nprevious-history (C-p)\r\nFetch the previous command from the history list, moving back in the list.\r\nnext-history (C-n)\r\nFetch the next command from the history list, moving forward in the list.\r\nbeginning-of-history (M-\u003c)\r\nMove to the first line in the history.\r\nend-of-history (M-\u003e)\r\nMove to the end of the input history, i.e., the line currently being entered.\r\nreverse-search-history (C-r)\r\nSearch backward starting at the current line and moving 'up' through the history as necessary. This is an\r\nincremental search.\r\nforward-search-history (C-s)\r\nSearch forward starting at the current line and moving 'down' through the history as necessary. This is an\r\nincremental search.\r\nnon-incremental-reverse-search-history (M-p)\r\nSearch backward through the history starting at the current line using a non-incremental search for a string\r\nsupplied by the user.\r\nnon-incremental-forward-search-history (M-n)\r\nSearch forward through the history using a non-incremental search for a string supplied by the user.\r\nhistory-search-forward\r\nSearch forward through the history for the string of characters between the start of the current line and the\r\npoint. This is a non-incremental search.\r\nhistory-search-backward\r\nSearch backward through the history for the string of characters between the start of the current line and\r\nthe point. This is a non-incremental search.\r\nyank-nth-arg (M-C-y)\r\nInsert the first argument to the previous command (usually the second word on the previous line) at point.\r\nWith an argument n, insert the nth word from the previous command (the words in the previous command\r\nbegin with word 0). A negative argument inserts the nth word from the end of the previous command. Once\r\nthe argument n is computed, the argument is extracted as if the \"!n\" history expansion had been specified.\r\nyank-last-arg (M-., M-_)\r\nInsert the last argument to the previous command (the last word of the previous history entry). With an\r\nargument, behave exactly like yank-nth-arg. Successive calls to yank-last-arg move back through the\r\nhistory list, inserting the last argument of each line in turn. The history expansion facilities are used to\r\nextract the last argument, as if the \"!$\" history expansion had been specified.\r\nshell-expand-line (M-C-e)\r\nExpand the line as the shell does. This performs alias and history expansion as well as all of the shell word\r\nexpansions. See HISTORY EXPANSION below for a description of history expansion.\r\nhttps://linux.die.net/man/1/bash\r\nPage 58 of 107\n\nhistory-expand-line (M-^)\r\nPerform history expansion on the current line. See HISTORY EXPANSION below for a description of history\r\nexpansion.\r\nmagic-space\r\nPerform history expansion on the current line and insert a space. See HISTORY EXPANSION below for a\r\ndescription of history expansion.\r\nalias-expand-line\r\nPerform alias expansion on the current line. See ALIASES above for a description of alias expansion.\r\nhistory-and-alias-expand-line\r\nPerform history and alias expansion on the current line.\r\ninsert-last-argument (M-., M-_)\r\nA synonym for yank-last-arg.\r\noperate-and-get-next (C-o)\r\nAccept the current line for execution and fetch the next line relative to the current line from the history for\r\nediting. Any argument is ignored.\r\nedit-and-execute-command (C-xC-e)\r\nInvoke an editor on the current command line, and execute the result as shell commands. Bash attempts to\r\ninvoke $VISUAL, $EDITOR, and emacs as the editor, in that order.\r\nCommands for Changing Text\r\ndelete-char (C-d)\r\nDelete the character at point. If point is at the beginning of the line, there are no characters in the line, and\r\nthe last character typed was not bound to delete-char, then return EOF.\r\nbackward-delete-char (Rubout)\r\nDelete the character behind the cursor. When given a numeric argument, save the deleted text on the kill\r\nring.\r\nforward-backward-delete-char\r\nDelete the character under the cursor, unless the cursor is at the end of the line, in which case the character\r\nbehind the cursor is deleted.\r\nquoted-insert (C-q, C-v)\r\nAdd the next character typed to the line verbatim. This is how to insert characters like C-q, for example.\r\ntab-insert (C-v TAB)\r\nInsert a tab character.\r\nself-insert (a, b, A, 1, !, ...)\r\nInsert the character typed.\r\ntranspose-chars (C-t)\r\nDrag the character before point forward over the character at point, moving point forward as well. If point\r\nis at the end of the line, then this transposes the two characters before point. Negative arguments have no\r\neffect.\r\ntranspose-words (M-t)\r\nDrag the word before point past the word after point, moving point over that word as well. If point is at the\r\nend of the line, this transposes the last two words on the line.\r\nhttps://linux.die.net/man/1/bash\r\nPage 59 of 107\n\nupcase-word (M-u)\r\nUppercase the current (or following) word. With a negative argument, uppercase the previous word, but do\r\nnot move point.\r\ndowncase-word (M-l)\r\nLowercase the current (or following) word. With a negative argument, lowercase the previous word, but do\r\nnot move point.\r\ncapitalize-word (M-c)\r\nCapitalize the current (or following) word. With a negative argument, capitalize the previous word, but do\r\nnot move point.\r\noverwrite-mode\r\nToggle overwrite mode. With an explicit positive numeric argument, switches to overwrite mode. With an\r\nexplicit non-positive numeric argument, switches to insert mode. This command affects only emacs mode;\r\nvi mode does overwrite differently. Each call to readline() starts in insert mode. In overwrite mode,\r\ncharacters bound to self-insert replace the text at point rather than pushing the text to the right. Characters\r\nbound to backward-delete-char replace the character before point with a space. By default, this command\r\nis unbound.\r\nKilling and Yanking\r\nkill-line (C-k)\r\nKill the text from point to the end of the line.\r\nbackward-kill-line (C-x Rubout)\r\nKill backward to the beginning of the line.\r\nunix-line-discard (C-u)\r\nKill backward from point to the beginning of the line. The killed text is saved on the kill-ring.\r\nkill-whole-line\r\nKill all characters on the current line, no matter where point is.\r\nkill-word (M-d)\r\nKill from point to the end of the current word, or if between words, to the end of the next word. Word\r\nboundaries are the same as those used by forward-word.\r\nbackward-kill-word (M-Rubout)\r\nKill the word behind point. Word boundaries are the same as those used by backward-word.\r\nshell-kill-word (M-d)\r\nKill from point to the end of the current word, or if between words, to the end of the next word. Word\r\nboundaries are the same as those used by shell-forward-word.\r\nshell-backward-kill-word (M-Rubout)\r\nKill the word behind point. Word boundaries are the same as those used by shell-backward-word.\r\nunix-word-rubout (C-w)\r\nKill the word behind point, using white space as a word boundary. The killed text is saved on the kill-ring.\r\nunix-filename-rubout\r\nKill the word behind point, using white space and the slash character as the word boundaries. The killed\r\ntext is saved on the kill-ring.\r\ndelete-horizontal-space (M-\\)\r\nhttps://linux.die.net/man/1/bash\r\nPage 60 of 107\n\nDelete all spaces and tabs around point.\r\nkill-region\r\nKill the text in the current region.\r\ncopy-region-as-kill\r\nCopy the text in the region to the kill buffer.\r\ncopy-backward-word\r\nCopy the word before point to the kill buffer. The word boundaries are the same as backward-word.\r\ncopy-forward-word\r\nCopy the word following point to the kill buffer. The word boundaries are the same as forward-word.\r\nyank (C-y)\r\nYank the top of the kill ring into the buffer at point.\r\nyank-pop (M-y)\r\nRotate the kill ring, and yank the new top. Only works following yank or yank-pop.\r\nNumeric Arguments\r\ndigit-argument (M-0, M-1, ..., M--)\r\nAdd this digit to the argument already accumulating, or start a new argument. M-- starts a negative\r\nargument.\r\nuniversal-argument\r\nThis is another way to specify an argument. If this command is followed by one or more digits, optionally\r\nwith a leading minus sign, those digits define the argument. If the command is followed by digits,\r\nexecuting universal-argument again ends the numeric argument, but is otherwise ignored. As a special\r\ncase, if this command is immediately followed by a character that is neither a digit or minus sign, the\r\nargument count for the next command is multiplied by four. The argument count is initially one, so\r\nexecuting this function the first time makes the argument count four, a second time makes the argument\r\ncount sixteen, and so on.\r\nCompleting\r\ncomplete (TAB)\r\nAttempt to perform completion on the text before point. Bash attempts completion treating the text as a\r\nvariable (if the text begins with $), username (if the text begins with ~), hostname (if the text begins with\r\n@), or command (including aliases and functions) in turn. If none of these produces a match, filename\r\ncompletion is attempted.\r\npossible-completions (M-?)\r\nList the possible completions of the text before point.\r\ninsert-completions (M-*)\r\nInsert all completions of the text before point that would have been generated by possible-completions.\r\nmenu-complete\r\nSimilar to complete, but replaces the word to be completed with a single match from the list of possible\r\ncompletions. Repeated execution of menu-complete steps through the list of possible completions,\r\ninserting each match in turn. At the end of the list of completions, the bell is rung (subject to the setting of\r\nbell-style) and the original text is restored. An argument of n moves n positions forward in the list of\r\nhttps://linux.die.net/man/1/bash\r\nPage 61 of 107\n\nmatches; a negative argument may be used to move backward through the list. This command is intended\r\nto be bound to TAB, but is unbound by default.\r\nc menu-complete-krd w\r\nIdentical to menu-complete, but moves backward through the list of possible completions, as if menu-complete had been given a negative argument. This command is unbound by default.\r\ndelete-char-or-list\r\nDeletes the character under the cursor if not at the beginning or end of the line (like delete-char). If at the\r\nend of the line, behaves identically to possible-completions. This command is unbound by default.\r\ncomplete-filename (M-/)\r\nAttempt filename completion on the text before point.\r\npossible-filename-completions (C-x /)\r\nList the possible completions of the text before point, treating it as a filename.\r\ncomplete-username (M-~)\r\nAttempt completion on the text before point, treating it as a username.\r\npossible-username-completions (C-x ~)\r\nList the possible completions of the text before point, treating it as a username.\r\ncomplete-variable (M-$)\r\nAttempt completion on the text before point, treating it as a shell variable.\r\npossible-variable-completions (C-x $)\r\nList the possible completions of the text before point, treating it as a shell variable.\r\ncomplete-hostname (M-@)\r\nAttempt completion on the text before point, treating it as a hostname.\r\npossible-hostname-completions (C-x @)\r\nList the possible completions of the text before point, treating it as a hostname.\r\ncomplete-command (M-!)\r\nAttempt completion on the text before point, treating it as a command name. Command completion\r\nattempts to match the text against aliases, reserved words, shell functions, shell builtins, and finally\r\nexecutable filenames, in that order.\r\npossible-command-completions (C-x !)\r\nList the possible completions of the text before point, treating it as a command name.\r\ndynamic-complete-history (M-TAB)\r\nAttempt completion on the text before point, comparing the text against lines from the history list for\r\npossible completion matches.\r\ndabbrev-expand\r\nAttempt menu completion on the text before point, comparing the text against lines from the history list for\r\npossible completion matches.\r\ncomplete-into-braces (M-{)\r\nPerform filename completion and insert the list of possible completions enclosed within braces so the list is\r\navailable to the shell (see Brace Expansion above).\r\nKeyboard Macros\r\nstart-kbd-macro (C-x ()\r\nhttps://linux.die.net/man/1/bash\r\nPage 62 of 107\n\nBegin saving the characters typed into the current keyboard macro.\r\nend-kbd-macro (C-x ))\r\nStop saving the characters typed into the current keyboard macro and store the definition.\r\ncall-last-kbd-macro (C-x e)\r\nRe-execute the last keyboard macro defined, by making the characters in the macro appear as if typed at\r\nthe keyboard.\r\nMiscellaneous\r\nre-read-init-file (C-x C-r)\r\nRead in the contents of the inputrc file, and incorporate any bindings or variable assignments found there.\r\nabort (C-g)\r\nAbort the current editing command and ring the terminal's bell (subject to the setting of bell-style).\r\ndo-uppercase-version (M-a, M-b, M-x, ...)\r\nIf the metafied character x is lowercase, run the command that is bound to the corresponding uppercase\r\ncharacter.\r\nprefix-meta (ESC)\r\nMetafy the next character typed. ESC f is equivalent to Meta-f.\r\nundo (C-_, C-x C-u)\r\nIncremental undo, separately remembered for each line.\r\nrevert-line (M-r)\r\nUndo all changes made to this line. This is like executing the undo command enough times to return the\r\nline to its initial state.\r\ntilde-expand (M-\u0026)\r\nPerform tilde expansion on the current word.\r\nset-mark (C-@, M-\u003cspace\u003e)\r\nSet the mark to the point. If a numeric argument is supplied, the mark is set to that position.\r\nexchange-point-and-mark (C-x C-x)\r\nSwap the point with the mark. The current cursor position is set to the saved position, and the old cursor\r\nposition is saved as the mark.\r\ncharacter-search (C-])\r\nA character is read and point is moved to the next occurrence of that character. A negative count searches\r\nfor previous occurrences.\r\ncharacter-search-backward (M-C-])\r\nA character is read and point is moved to the previous occurrence of that character. A negative count\r\nsearches for subsequent occurrences.\r\nskip-csi-sequence ()\r\nRead enough characters to consume a multi-key sequence such as those defined for keys like Home and\r\nEnd. Such sequences begin with a Control Sequence Indicator (CSI), usually ESC-[. If this sequence is\r\nbound to \"\\[\", keys producing such sequences will have no effect unless explicitly bound to a readline\r\ncommand, instead of inserting stray characters into the editing buffer. This is unbound by default, but\r\nusually bound to ESC-[.\r\ninsert-comment (M-#)\r\nhttps://linux.die.net/man/1/bash\r\nPage 63 of 107\n\nWithout a numeric argument, the value of the readline comment-begin variable is inserted at the beginning\r\nof the current line. If a numeric argument is supplied, this command acts as a toggle: if the characters at the\r\nbeginning of the line do not match the value of comment-begin, the value is inserted, otherwise the\r\ncharacters in comment-begin are deleted from the beginning of the line. In either case, the line is accepted\r\nas if a newline had been typed. The default value of comment-begin causes this command to make the\r\ncurrent line a shell comment. If a numeric argument causes the comment character to be removed, the line\r\nwill be executed by the shell.\r\nglob-complete-word (M-g)\r\nThe word before point is treated as a pattern for pathname expansion, with an asterisk implicitly appended.\r\nThis pattern is used to generate a list of matching file names for possible completions.\r\nglob-expand-word (C-x *)\r\nThe word before point is treated as a pattern for pathname expansion, and the list of matching file names is\r\ninserted, replacing the word. If a numeric argument is supplied, an asterisk is appended before pathname\r\nexpansion.\r\nglob-list-expansions (C-x g)\r\nThe list of expansions that would have been generated by glob-expand-word is displayed, and the line is\r\nredrawn. If a numeric argument is supplied, an asterisk is appended before pathname expansion.\r\ndump-functions\r\nPrint all of the functions and their key bindings to the readline output stream. If a numeric argument is\r\nsupplied, the output is formatted in such a way that it can be made part of an inputrc file.\r\ndump-variables\r\nPrint all of the settable readline variables and their values to the readline output stream. If a numeric\r\nargument is supplied, the output is formatted in such a way that it can be made part of an inputrc file.\r\ndump-macros\r\nPrint all of the readline key sequences bound to macros and the strings they output. If a numeric argument\r\nis supplied, the output is formatted in such a way that it can be made part of an inputrc file.\r\ndisplay-shell-version (C-x C-v)\r\nDisplay version information about the current instance of bash.\r\nProgrammable Completion\r\nWhen word completion is attempted for an argument to a command for which a completion specification (a\r\ncompspec) has been defined using the complete builtin (see SHELL BUILTIN COMMANDS below), the\r\nprogrammable completion facilities are invoked.\r\nFirst, the command name is identified. If the command word is the empty string (completion attempted at the\r\nbeginning of an empty line), any compspec defined with the -E option to complete is used. If a compspec has\r\nbeen defined for that command, the compspec is used to generate the list of possible completions for the word. If\r\nthe command word is a full pathname, a compspec for the full pathname is searched for first. If no compspec is\r\nfound for the full pathname, an attempt is made to find a compspec for the portion following the final slash. If\r\nthose searches to not result in a compspec, any compspec defined with the -D option to complete is used as the\r\ndefault.\r\nhttps://linux.die.net/man/1/bash\r\nPage 64 of 107\n\nOnce a compspec has been found, it is used to generate the list of matching words. If a compspec is not found, the\r\ndefault bash completion as described above under Completing is performed.\r\nFirst, the actions specified by the compspec are used. Only matches which are prefixed by the word being\r\ncompleted are returned. When the -f or -d option is used for filename or directory name completion, the shell\r\nvariable FIGNORE is used to filter the matches.\r\nAny completions specified by a pathname expansion pattern to the -G option are generated next. The words\r\ngenerated by the pattern need not match the word being completed. The GLOBIGNORE shell variable is not used to\r\nfilter the matches, but the FIGNORE variable is used.\r\nNext, the string specified as the argument to the -W option is considered. The string is first split using the\r\ncharacters in the IFS special variable as delimiters. Shell quoting is honored. Each word is then expanded using\r\nbrace expansion, tilde expansion, parameter and variable expansion, command substitution, and arithmetic\r\nexpansion, as described above under EXPANSION. The results are split using the rules described above under\r\nWord Splitting. The results of the expansion are prefix-matched against the word being completed, and the\r\nmatching words become the possible completions.\r\nAfter these matches have been generated, any shell function or command specified with the -F and -C options is\r\ninvoked. When the command or function is invoked, the COMP_LINE, COMP_POINT, COMP_KEY, and\r\nCOMP_TYPE variables are assigned values as described above under Shell Variables. If a shell function is being\r\ninvoked, the COMP_WORDS and COMP_CWORD variables are also set. When the function or command is invoked,\r\nthe first argument is the name of the command whose arguments are being completed, the second argument is the\r\nword being completed, and the third argument is the word preceding the word being completed on the current\r\ncommand line. No filtering of the generated completions against the word being completed is performed; the\r\nfunction or command has complete freedom in generating the matches.\r\nAny function specified with -F is invoked first. The function may use any of the shell facilities, including the\r\ncompgen builtin described below, to generate the matches. It must put the possible completions in the\r\nCOMPREPLY array variable.\r\nNext, any command specified with the -C option is invoked in an environment equivalent to command\r\nsubstitution. It should print a list of completions, one per line, to the standard output. Backslash may be used to\r\nescape a newline, if necessary.\r\nAfter all of the possible completions are generated, any filter specified with the -X option is applied to the list. The\r\nfilter is a pattern as used for pathname expansion; a \u0026 in the pattern is replaced with the text of the word being\r\ncompleted. A literal \u0026 may be escaped with a backslash; the backslash is removed before attempting a match. Any\r\ncompletion that matches the pattern will be removed from the list. A leading ! negates the pattern; in this case any\r\ncompletion not matching the pattern will be removed.\r\nFinally, any prefix and suffix specified with the -P and -S options are added to each member of the completion\r\nlist, and the result is returned to the readline completion code as the list of possible completions.\r\nIf the previously-applied actions do not generate any matches, and the -o dirnames option was supplied to\r\ncomplete when the compspec was defined, directory name completion is attempted.\r\nhttps://linux.die.net/man/1/bash\r\nPage 65 of 107\n\nIf the -o plusdirs option was supplied to complete when the compspec was defined, directory name completion is\r\nattempted and any matches are added to the results of the other actions.\r\nBy default, if a compspec is found, whatever it generates is returned to the completion code as the full set of\r\npossible completions. The default bash completions are not attempted, and the readline default of filename\r\ncompletion is disabled. If the -o bashdefault option was supplied to complete when the compspec was defined,\r\nthe bash default completions are attempted if the compspec generates no matches. If the -o default option was\r\nsupplied to complete when the compspec was defined, readline's default completion will be performed if the\r\ncompspec (and, if attempted, the default bash completions) generate no matches.\r\nWhen a compspec indicates that directory name completion is desired, the programmable completion functions\r\nforce readline to append a slash to completed names which are symbolic links to directories, subject to the value\r\nof the mark-directories readline variable, regardless of the setting of the mark-symlinked-directories readline\r\nvariable.\r\nThere is some support for dynamically modifying completions. This is most useful when used in combination with\r\na default completion specified with complete -D. It's possible for shell functions executed as completion handlers\r\nto indicate that completion should be retried by returning an exit status of 124. If a shell function returns 124, and\r\nchanges the compspec associated with the command on which completion is being attempted (supplied as the first\r\nargument when the function is executed), programmable completion restarts from the beginning, with an attempt\r\nto find a compspec for that command. This allows a set of completions to be built dynamically as completion is\r\nattempted, rather than being loaded all at once.\r\nFor instance, assuming that there is a library of compspecs, each kept in a file corresponding to the name of the\r\ncommand, the following default completion function would load completions dynamically:\r\n_completion_loader()\r\n{\r\n. \"/etc/bash_completion.d/$1.sh\" \u003e/dev/null 2\u003e\u00261 \u0026\u0026 return 124\r\n}\r\ncomplete -D -F _completion_loader\r\nHistory\r\nWhen the -o history option to the set builtin is enabled, the shell provides access to the command history, the list\r\nof commands previously typed. The value of the HISTSIZE variable is used as the number of commands to save in\r\na history list. The text of the last HISTSIZE commands (default 500) is saved. The shell stores each command in\r\nthe history list prior to parameter and variable expansion (see EXPANSION above) but after history expansion is\r\nperformed, subject to the values of the shell variables HISTIGNORE and HISTCONTROL.\r\nOn startup, the history is initialized from the file named by the variable HISTFILE (default ~/.bash_history). The\r\nfile named by the value of HISTFILE is truncated, if necessary, to contain no more than the number of lines\r\nspecified by the value of HISTFILESIZE. When the history file is read, lines beginning with the history comment\r\ncharacter followed immediately by a digit are interpreted as timestamps for the preceding history line. These\r\nhttps://linux.die.net/man/1/bash\r\nPage 66 of 107\n\ntimestamps are optionally displayed depending on the value of the HISTTIMEFORMAT variable. When an\r\ninteractive shell exits, the last $HISTSIZE lines are copied from the history list to $HISTFILE. If the histappend\r\nshell option is enabled (see the description of shopt under SHELL BUILTIN COMMANDS below), the lines are\r\nappended to the history file, otherwise the history file is overwritten. If HISTFILE is unset, or if the history file is\r\nunwritable, the history is not saved. If the HISTTIMEFORMAT variable is set, time stamps are written to the history\r\nfile, marked with the history comment character, so they may be preserved across shell sessions. This uses the\r\nhistory comment character to distinguish timestamps from other history lines. After saving the history, the history\r\nfile is truncated to contain no more than HISTFILESIZE lines. If HISTFILESIZE is not set, no truncation is\r\nperformed.\r\nThe builtin command fc (see SHELL BUILTIN COMMANDS below) may be used to list or edit and re-execute a\r\nportion of the history list. The history builtin may be used to display or modify the history list and manipulate the\r\nhistory file. When using command-line editing, search commands are available in each editing mode that provide\r\naccess to the history list.\r\nThe shell allows control over which commands are saved on the history list. The HISTCONTROL and\r\nHISTIGNORE variables may be set to cause the shell to save only a subset of the commands entered. The cmdhist\r\nshell option, if enabled, causes the shell to attempt to save each line of a multi-line command in the same history\r\nentry, adding semicolons where necessary to preserve syntactic correctness. The lithist shell option causes the\r\nshell to save the command with embedded newlines instead of semicolons. See the description of the shopt builtin\r\nbelow under SHELL BUILTIN COMMANDS for information on setting and unsetting shell options.\r\nHistory Expansion\r\nThe shell supports a history expansion feature that is similar to the history expansion in csh. This section describes\r\nwhat syntax features are available. This feature is enabled by default for interactive shells, and can be disabled\r\nusing the +H option to the set builtin command (see SHELL BUILTIN COMMANDS below). Non-interactive shells\r\ndo not perform history expansion by default.\r\nHistory expansions introduce words from the history list into the input stream, making it easy to repeat\r\ncommands, insert the arguments to a previous command into the current input line, or fix errors in previous\r\ncommands quickly.\r\nHistory expansion is performed immediately after a complete line is read, before the shell breaks it into words. It\r\ntakes place in two parts. The first is to determine which line from the history list to use during substitution. The\r\nsecond is to select portions of that line for inclusion into the current one. The line selected from the history is the\r\nevent, and the portions of that line that are acted upon are words. Various modifiers are available to manipulate the\r\nselected words. The line is broken into words in the same fashion as when reading input, so that several\r\nmetacharacter-separated words surrounded by quotes are considered one word. History expansions are introduced\r\nby the appearance of the history expansion character, which is ! by default. Only backslash (\\) and single quotes\r\ncan quote the history expansion character.\r\nSeveral characters inhibit history expansion if found immediately following the history expansion character, even\r\nif it is unquoted: space, tab, newline, carriage return, and =. If the extglob shell option is enabled, ( will also\r\nhttps://linux.die.net/man/1/bash\r\nPage 67 of 107\n\ninhibit expansion.\r\nSeveral shell options settable with the shopt builtin may be used to tailor the behavior of history expansion. If the\r\nhistverify shell option is enabled (see the description of the shopt builtin below), and readline is being used,\r\nhistory substitutions are not immediately passed to the shell parser. Instead, the expanded line is reloaded into the\r\nreadline editing buffer for further modification. If readline is being used, and the histreedit shell option is\r\nenabled, a failed history substitution will be reloaded into the readline editing buffer for correction. The -p option\r\nto the history builtin command may be used to see what a history expansion will do before using it. The -s option\r\nto the history builtin may be used to add commands to the end of the history list without actually executing them,\r\nso that they are available for subsequent recall.\r\nThe shell allows control of the various characters used by the history expansion mechanism (see the description of\r\nhistchars above under Shell Variables). The shell uses the history comment character to mark history timestamps\r\nwhen writing the history file.\r\nEvent Designators\r\nAn event designator is a reference to a command line entry in the history list.\r\n!\r\nStart a history substitution, except when followed by a blank, newline, carriage return, = or ( (when the extglob\r\nshell option is enabled using the shopt builtin).\r\n!n\r\nRefer to command line n.\r\n!-n\r\nRefer to the current command line minus n.\r\n!!\r\nRefer to the previous command. This is a synonym for '!-1'.\r\n!string\r\nRefer to the most recent command starting with string.\r\n!?string[?]\r\nRefer to the most recent command containing string. The trailing ? may be omitted if string is followed\r\nimmediately by a newline.\r\n^ string1 ^ string2 ^\r\nQuick substitution. Repeat the last command, replacing string1 with string2. Equivalent to\r\n''!!:s/string1/string2/'' (see Modifiers below).\r\n!#\r\nThe entire command line typed so far.\r\nhttps://linux.die.net/man/1/bash\r\nPage 68 of 107\n\nWord Designators\r\nWord designators are used to select desired words from the event. A : separates the event specification from the\r\nword designator. It may be omitted if the word designator begins with a ^, $, *, -, or %. Words are numbered from\r\nthe beginning of the line, with the first word being denoted by 0 (zero). Words are inserted into the current line\r\nseparated by single spaces.\r\n0 (zero)\r\nThe zeroth word. For the shell, this is the command word.\r\nn\r\nThe nth word.\r\n^\r\nThe first argument. That is, word 1.\r\n$\r\nThe last argument.\r\n%\r\nThe word matched by the most recent '?string?' search.\r\nx-y\r\nA range of words; '-y' abbreviates '0-y'.\r\n*\r\nAll of the words but the zeroth. This is a synonym for '1-$'. It is not an error to use * if there is just one word in\r\nthe event; the empty string is returned in that case.\r\nx*\r\nAbbreviates x-$.\r\nx-Abbreviates x-$ like x*, but omits the last word.\r\nIf a word designator is supplied without an event specification, the previous command is used as the event.\r\nModifiers\r\nAfter the optional word designator, there may appear a sequence of one or more of the following modifiers, each\r\npreceded by a ':'.\r\nh\r\nRemove a trailing file name component, leaving only the head.\r\nhttps://linux.die.net/man/1/bash\r\nPage 69 of 107\n\nt\r\nRemove all leading file name components, leaving the tail.\r\nr\r\nRemove a trailing suffix of the form .xxx, leaving the basename.\r\ne\r\nRemove all but the trailing suffix.\r\np\r\nPrint the new command but do not execute it.\r\nq\r\nQuote the substituted words, escaping further substitutions.\r\nx\r\nQuote the substituted words as with q, but break into words at blanks and newlines.\r\ns/old/new/\r\nSubstitute new for the first occurrence of old in the event line. Any delimiter can be used in place of /. The\r\nfinal delimiter is optional if it is the last character of the event line. The delimiter may be quoted in old and\r\nnew with a single backslash. If \u0026 appears in new, it is replaced by old. A single backslash will quote the \u0026.\r\nIf old is null, it is set to the last old substituted, or, if no previous history substitutions took place, the last\r\nstring in a !?string[?] search.\r\n\u0026\r\nRepeat the previous substitution.\r\ng\r\nCause changes to be applied over the entire event line. This is used in conjunction with ':s' (e.g., ':gs/old/new/') or\r\n':\u0026'. If used with ':s', any delimiter can be used in place of /, and the final delimiter is optional if it is the last\r\ncharacter of the event line. An a may be used as a synonym for g.\r\nG\r\nApply the following 's' modifier once to each word in the event line.\r\nShell Builtin Commands\r\nUnless otherwise noted, each builtin command documented in this section as accepting options preceded by -\r\naccepts -- to signify the end of the options. The :, true, false, and test builtins do not accept options and do not\r\ntreat -- specially. The exit, logout, break, continue, let, and shift builtins accept and process arguments beginning\r\nhttps://linux.die.net/man/1/bash\r\nPage 70 of 107\n\nwith - without requiring --. Other builtins that accept arguments but are not specified as accepting options interpret\r\narguments beginning with - as invalid options and require -- to prevent this interpretation.\r\n: [arguments]\r\nNo effect; the command does nothing beyond expanding arguments and performing any specified\r\nredirections. A zero exit code is returned.\r\n. filename [arguments]\r\nsource filename [arguments]\r\nRead and execute commands from filename in the current shell environment and return the exit status of\r\nthe last command executed from filename. If filename does not contain a slash, file names in PATH are used\r\nto find the directory containing filename. The file searched for in PATH need not be executable. When bash\r\nis not in posix mode, the current directory is searched if no file is found in PATH. If the sourcepath option\r\nto the shopt builtin command is turned off, the PATH is not searched. If any arguments are supplied, they\r\nbecome the positional parameters when filename is executed. Otherwise the positional parameters are\r\nunchanged. The return status is the status of the last command exited within the script (0 if no commands\r\nare executed), and false if filename is not found or cannot be read.\r\nalias [-p] [name[=value] ...]\r\nAlias with no arguments or with the -p option prints the list of aliases in the form alias name=value on\r\nstandard output. When arguments are supplied, an alias is defined for each name whose value is given. A\r\ntrailing space in value causes the next word to be checked for alias substitution when the alias is expanded.\r\nFor each name in the argument list for which no value is supplied, the name and value of the alias is\r\nprinted. Alias returns true unless a name is given for which no alias has been defined.\r\nbg [jobspec ...]\r\nResume each suspended job jobspec in the background, as if it had been started with \u0026. If jobspec is not\r\npresent, the shell's notion of the current job is used. bg jobspec returns 0 unless run when job control is\r\ndisabled or, when run with job control enabled, any specified jobspec was not found or was started without\r\njob control.\r\nbind [-m keymap] [-lpsvPSV]\r\nbind [-m keymap] [-q function] [-u function] [-r keyseq]\r\nbind [-m keymap] -f filename\r\nbind [-m keymap] -x keyseq:shell-command\r\nbind [-m keymap] keyseq:function-name\r\nbind readline-command\r\nDisplay current readline key and function bindings, bind a key sequence to a readline function or macro,\r\nor set a readline variable. Each non-option argument is a command as it would appear in .inputrc, but each\r\nbinding or command must be passed as a separate argument; e.g., '\"\\C-x\\C-r\": re-read-init-file'. Options, if\r\nsupplied, have the following meanings:\r\n-m keymap\r\nUse keymap as the keymap to be affected by the subsequent bindings. Acceptable keymap names are emacs,\r\nemacs-standard, emacs-meta, emacs-ctlx, vi, vi-move, vi-command, and vi-insert. vi is equivalent to vi-command;\r\nemacs is equivalent to emacs-standard.\r\nhttps://linux.die.net/man/1/bash\r\nPage 71 of 107\n\n-l\r\nList the names of all readline functions.\r\n-p\r\nDisplay readline function names and bindings in such a way that they can be re-read.\r\n-P\r\nList current readline function names and bindings.\r\n-s\r\nDisplay readline key sequences bound to macros and the strings they output in such a way that they can be\r\nre-read.\r\n-S\r\nDisplay readline key sequences bound to macros and the strings they output.\r\n-v\r\nDisplay readline variable names and values in such a way that they can be re-read.\r\n-V\r\nList current readline variable names and values.\r\n-f filename\r\nRead key bindings from filename.\r\n-q function\r\nQuery about which keys invoke the named function.\r\n-u function\r\nUnbind all keys bound to the named function.\r\n-r keyseq\r\nRemove any current binding for keyseq.\r\n-x keyseq:shell-command\r\nCause shell-command to be executed whenever keyseq is entered. When shell-command is executed, the shell sets\r\nthe READLINE_LINE variable to the contents of the readline line buffer and the READLINE_POINT variable to the\r\ncurrent location of the insertion point. If the executed command changes the value of READLINE_LINE or\r\nREADLINE_POINT, those new values will be reflected in the editing state.\r\nhttps://linux.die.net/man/1/bash\r\nPage 72 of 107\n\nThe return value is 0 unless an unrecognized option is given or an error occurred.\r\nbreak [n]\r\nExit from within a for, while, until, or select loop. If n is specified, break n levels. n must be ≥ 1. If n is\r\ngreater than the number of enclosing loops, all enclosing loops are exited. The return value is non-zero\r\nwhen n is ≤ 0; Otherwise, break returns 0 value.\r\nbuiltin shell-builtin [arguments]\r\nExecute the specified shell builtin, passing it arguments, and return its exit status. This is useful when\r\ndefining a function whose name is the same as a shell builtin, retaining the functionality of the builtin\r\nwithin the function. The cd builtin is commonly redefined this way. The return status is false if shell-builtin\r\nis not a shell builtin command.\r\ncaller [expr]\r\nReturns the context of any active subroutine call (a shell function or a script executed with the . or source\r\nbuiltins. Without expr, caller displays the line number and source filename of the current subroutine call. If\r\na non-negative integer is supplied as expr, caller displays the line number, subroutine name, and source file\r\ncorresponding to that position in the current execution call stack. This extra information may be used, for\r\nexample, to print a stack trace. The current frame is frame 0. The return value is 0 unless the shell is not\r\nexecuting a subroutine call or expr does not correspond to a valid position in the call stack.\r\ncd [-L|-P] [dir]\r\nChange the current directory to dir. The variable HOME is the default dir. The variable CDPATH defines the\r\nsearch path for the directory containing dir. Alternative directory names in CDPATH are separated by a\r\ncolon (:). A null directory name in CDPATH is the same as the current directory, i.e., ''.''. If dir begins with a\r\nslash (/), then CDPATH is not used. The -P option says to use the physical directory structure instead of\r\nfollowing symbolic links (see also the -P option to the set builtin command); the -L option forces symbolic\r\nlinks to be followed. An argument of - is equivalent to $OLDPWD. If a non-empty directory name from\r\nCDPATH is used, or if - is the first argument, and the directory change is successful, the absolute pathname\r\nof the new working directory is written to the standard output. The return value is true if the directory was\r\nsuccessfully changed; false otherwise.\r\ncommand [-pVv] command [arg ...]\r\nRun command with args suppressing the normal shell function lookup. Only builtin commands or\r\ncommands found in the PATH are executed. If the -p option is given, the search for command is performed\r\nusing a default value for PATH that is guaranteed to find all of the standard utilities. If either the -V or -v\r\noption is supplied, a description of command is printed. The -v option causes a single word indicating the\r\ncommand or file name used to invoke command to be displayed; the -V option produces a more verbose\r\ndescription. If the -V or -v option is supplied, the exit status is 0 if command was found, and 1 if not. If\r\nneither option is supplied and an error occurred or command cannot be found, the exit status is 127.\r\nOtherwise, the exit status of the command builtin is the exit status of command.\r\ncompgen [option] [word]\r\nGenerate possible completion matches for word according to the options, which may be any option\r\naccepted by the complete builtin with the exception of -p and -r, and write the matches to the standard\r\noutput. When using the -F or -C options, the various shell variables set by the programmable completion\r\nfacilities, while available, will not have useful values.\r\nhttps://linux.die.net/man/1/bash\r\nPage 73 of 107\n\nThe matches will be generated in the same way as if the programmable completion code had generated\r\nthem directly from a completion specification with the same flags. If word is specified, only those\r\ncompletions matching word will be displayed.\r\nThe return value is true unless an invalid option is supplied, or no matches were generated.\r\ncomplete [-abcdefgjksuv] [-o comp-option] [-DE] [-A action] [-G globpat] [-W wordlist] [-F function] [-C\r\ncommand]\r\n[-X filterpat] [-P prefix] [-S suffix] name [name ...]\r\ncomplete -pr [-DE] [name ...]\r\nSpecify how arguments to each name should be completed. If the -p option is supplied, or if no options are\r\nsupplied, existing completion specifications are printed in a way that allows them to be reused as input.\r\nThe -r option removes a completion specification for each name, or, if no names are supplied, all\r\ncompletion specifications. The -D option indicates that the remaining options and actions should apply to\r\nthe ''default'' command completion; that is, completion attempted on a command for which no completion\r\nhas previously been defined. The -E option indicates that the remaining options and actions should apply to\r\n''empty'' command completion; that is, completion attempted on a blank line.\r\nThe process of applying these completion specifications when word completion is attempted is described\r\nabove under Programmable Completion.\r\nOther options, if specified, have the following meanings. The arguments to the -G, -W, and -X options\r\n(and, if necessary, the -P and -S options) should be quoted to protect them from expansion before the\r\ncomplete builtin is invoked.\r\n-o comp-option\r\nThe comp-option controls several aspects of the compspec's behavior beyond the simple generation of\r\ncompletions. comp-option may be one of:\r\nbashdefault\r\nPerform the rest of the default bash completions if the compspec generates no matches.\r\ndefault\r\nUse readline's default filename completion if the compspec generates no matches.\r\ndirnames\r\nPerform directory name completion if the compspec generates no matches.\r\nfilenames\r\nTell readline that the compspec generates filenames, so it can perform any filename-specific processing (like\r\nadding a slash to directory names, quoting special characters, or suppressing trailing spaces). Intended to be used\r\nwith shell functions.\r\nhttps://linux.die.net/man/1/bash\r\nPage 74 of 107\n\nnospace\r\nTell readline not to append a space (the default) to words completed at the end of the line.\r\nplusdirs\r\nAfter any matches defined by the compspec are generated, directory name completion is attempted and any\r\nmatches are added to the results of the other actions.\r\n-A action\r\nThe action may be one of the following to generate a list of possible completions:\r\nalias\r\nAlias names. May also be specified as -a.\r\narrayvar\r\nArray variable names.\r\nbinding\r\nReadline key binding names.\r\nbuiltin\r\nNames of shell builtin commands. May also be specified as -b.\r\ncommand\r\nCommand names. May also be specified as -c.\r\ndirectory\r\nDirectory names. May also be specified as -d.\r\ndisabled\r\nNames of disabled shell builtins.\r\nenabled\r\nNames of enabled shell builtins.\r\nexport\r\nNames of exported shell variables. May also be specified as -e.\r\nfile\r\nFile names. May also be specified as -f.\r\nhttps://linux.die.net/man/1/bash\r\nPage 75 of 107\n\nfunction\r\nNames of shell functions.\r\ngroup\r\nGroup names. May also be specified as -g.\r\nhelptopic\r\nHelp topics as accepted by the help builtin.\r\nhostname\r\nHostnames, as taken from the file specified by the HOSTFILE shell variable.\r\njob\r\nJob names, if job control is active. May also be specified as -j.\r\nkeyword\r\nShell reserved words. May also be specified as -k.\r\nrunning\r\nNames of running jobs, if job control is active.\r\nservice\r\nService names. May also be specified as -s.\r\nsetopt\r\nValid arguments for the -o option to the set builtin.\r\nshopt\r\nShell option names as accepted by the shopt builtin.\r\nsignal\r\nSignal names.\r\nstopped\r\nNames of stopped jobs, if job control is active.\r\nuser\r\nUser names. May also be specified as -u.\r\nhttps://linux.die.net/man/1/bash\r\nPage 76 of 107\n\nvariable\r\nNames of all shell variables. May also be specified as -v.\r\n-G globpat\r\nThe pathname expansion pattern globpat is expanded to generate the possible completions.\r\n-W wordlist\r\nThe wordlist is split using the characters in the IFS special variable as delimiters, and each resultant word is\r\nexpanded. The possible completions are the members of the resultant list which match the word being completed.\r\n-C command\r\ncommand is executed in a subshell environment, and its output is used as the possible completions.\r\n-F function\r\nThe shell function function is executed in the current shell environment. When it finishes, the possible\r\ncompletions are retrieved from the value of the COMPREPLY array variable.\r\n-X filterpat\r\nfilterpat is a pattern as used for pathname expansion. It is applied to the list of possible completions generated by\r\nthe preceding options and arguments, and each completion matching filterpat is removed from the list. A leading !\r\nin filterpat negates the pattern; in this case, any completion not matching filterpat is removed.\r\n-P prefix\r\nprefix is added at the beginning of each possible completion after all other options have been applied.\r\n-S suffix\r\nsuffix is appended to each possible completion after all other options have been applied.\r\nThe return value is true unless an invalid option is supplied, an option other than -p or -r is supplied\r\nwithout a name argument, an attempt is made to remove a completion specification for a name for which\r\nno specification exists, or an error occurs adding a completion specification.\r\ncompopt [-o option] [-DE] [+o option] [name]\r\nModify completion options for each name according to the options, or for the currently-execution\r\ncompletion if no names are supplied. If no options are given, display the completion options for each name\r\nor the current completion. The possible values of option are those valid for the complete builtin described\r\nabove. The -D option indicates that the remaining options should apply to the ''default'' command\r\ncompletion; that is, completion attempted on a command for which no completion has previously been\r\ndefined. The -E option indicates that the remaining options should apply to ''empty'' command completion;\r\nthat is, completion attempted on a blank line.\r\nhttps://linux.die.net/man/1/bash\r\nPage 77 of 107\n\nThe return value is true unless an invalid option is supplied, an attempt is made to modify the options for a name\r\nfor which no completion specification exists, or an output error occurs.\r\ncontinue [n]\r\nResume the next iteration of the enclosing for, while, until, or select loop. If n is specified, resume at the\r\nnth enclosing loop. n must be ≥ 1. If n is greater than the number of enclosing loops, the last enclosing loop\r\n(the ''top-level'' loop) is resumed. When continue is executed inside of loop, the return value is non-zero\r\nwhen n is ≤ 0; Otherwise, continue returns 0 value. When continue is executed outside of loop, the return\r\nvalue is 0.\r\ndeclare [-aAfFilrtux] [-p] [name[=value] ...]\r\ntypeset [-aAfFilrtux] [-p] [name[=value] ...]\r\nDeclare variables and/or give them attributes. If no names are given then display the values of variables.\r\nThe -p option will display the attributes and values of each name. When -p is used with name arguments,\r\nadditional options are ignored. When -p is supplied without name arguments, it will display the attributes\r\nand values of all variables having the attributes specified by the additional options. If no other options are\r\nsupplied with -p, declare will display the attributes and values of all shell variables. The -f option will\r\nrestrict the display to shell functions. The -F option inhibits the display of function definitions; only the\r\nfunction name and attributes are printed. If the extdebug shell option is enabled using shopt, the source\r\nfile name and line number where the function is defined are displayed as well. The -F option implies -f.\r\nThe following options can be used to restrict output to variables with the specified attribute or to give\r\nvariables attributes:\r\n-a\r\nEach name is an indexed array variable (see Arrays above).\r\n-A\r\nEach name is an associative array variable (see Arrays above).\r\n-f\r\nUse function names only.\r\n-i\r\nThe variable is treated as an integer; arithmetic evaluation (see ARITHMETIC EVALUATION above) is\r\nperformed when the variable is assigned a value.\r\n-l\r\nWhen the variable is assigned a value, all upper-case characters are converted to lower-case. The upper-case attribute is disabled.\r\n-r\r\nMake names readonly. These names cannot then be assigned values by subsequent assignment statements\r\nor unset.\r\nhttps://linux.die.net/man/1/bash\r\nPage 78 of 107\n\n-t\r\nGive each name the trace attribute. Traced functions inherit the DEBUG and RETURN traps from the\r\ncalling shell. The trace attribute has no special meaning for variables.\r\n-u\r\nWhen the variable is assigned a value, all lower-case characters are converted to upper-case. The lower-case attribute is disabled.\r\n-x\r\nMark names for export to subsequent commands via the environment.\r\nUsing '+' instead of '-' turns off the attribute instead, with the exceptions that +a may not be used to destroy\r\nan array variable and +r will not remove the readonly attribute. When used in a function, makes each name\r\nlocal, as with the local command. If a variable name is followed by =value, the value of the variable is set\r\nto value. The return value is 0 unless an invalid option is encountered, an attempt is made to define a\r\nfunction using ''-f foo=bar'', an attempt is made to assign a value to a readonly variable, an attempt is made\r\nto assign a value to an array variable without using the compound assignment syntax (see Arrays above),\r\none of the names is not a valid shell variable name, an attempt is made to turn off readonly status for a\r\nreadonly variable, an attempt is made to turn off array status for an array variable, or an attempt is made to\r\ndisplay a non-existent function with -f.\r\ndirs [+n] [-n] [-cplv]\r\nWithout options, displays the list of currently remembered directories. The default display is on a single\r\nline with directory names separated by spaces. Directories are added to the list with the pushd command;\r\nthe popd command removes entries from the list.\r\n+n\r\nDisplays the nth entry counting from the left of the list shown by dirs when invoked without options,\r\nstarting with zero.\r\n-n\r\nDisplays the nth entry counting from the right of the list shown by dirs when invoked without options,\r\nstarting with zero.\r\n-c\r\nClears the directory stack by deleting all of the entries.\r\n-l\r\nProduces a longer listing; the default listing format uses a tilde to denote the home directory.\r\n-p\r\nPrint the directory stack with one entry per line.\r\nhttps://linux.die.net/man/1/bash\r\nPage 79 of 107\n\n-v\r\nPrint the directory stack with one entry per line, prefixing each entry with its index in the stack.\r\nThe return value is 0 unless an invalid option is supplied or n indexes beyond the end of the directory\r\nstack.\r\ndisown [-ar] [-h] [jobspec ...]\r\nWithout options, each jobspec is removed from the table of active jobs. If jobspec is not present, and\r\nneither -a nor -r is supplied, the shell's notion of the current job is used. If the -h option is given, each\r\njobspec is not removed from the table, but is marked so that SIGHUP is not sent to the job if the shell\r\nreceives a SIGHUP. If no jobspec is present, and neither the -a nor the -r option is supplied, the current job\r\nis used. If no jobspec is supplied, the -a option means to remove or mark all jobs; the -r option without a\r\njobspec argument restricts operation to running jobs. The return value is 0 unless a jobspec does not specify\r\na valid job.\r\necho [-neE] [arg ...]\r\nOutput the args, separated by spaces, followed by a newline. The return status is always 0. If -n is\r\nspecified, the trailing newline is suppressed. If the -e option is given, interpretation of the following\r\nbackslash-escaped characters is enabled. The -E option disables the interpretation of these escape\r\ncharacters, even on systems where they are interpreted by default. The xpg_echo shell option may be used\r\nto dynamically determine whether or not echo expands these escape characters by default. echo does not\r\ninterpret -- to mean the end of options. echo interprets the following escape sequences:\r\n\\a\r\nalert (bell)\r\n\\b\r\nbackspace\r\n\\c\r\nsuppress further output\r\n\\e\r\nan escape character\r\n\\f\r\nform feed\r\n\\n\r\nnew line\r\n\\r\r\ncarriage return\r\nhttps://linux.die.net/man/1/bash\r\nPage 80 of 107\n\n\\t\r\nhorizontal tab\r\n\\v\r\nvertical tab\r\n\\\\\r\nbackslash\r\n\\0nnn\r\nthe eight-bit character whose value is the octal value nnn (zero to three octal digits)\r\n\\xHH\r\nthe eight-bit character whose value is the hexadecimal value HH (one or two hex digits)\r\nenable [-a] [-dnps] [-f filename] [name ...]\r\nEnable and disable builtin shell commands. Disabling a builtin allows a disk command which has the same\r\nname as a shell builtin to be executed without specifying a full pathname, even though the shell normally\r\nsearches for builtins before disk commands. If -n is used, each name is disabled; otherwise, names are\r\nenabled. For example, to use the test binary found via the PATH instead of the shell builtin version, run\r\n''enable -n test''. The -f option means to load the new builtin command name from shared object filename,\r\non systems that support dynamic loading. The -d option will delete a builtin previously loaded with -f. If\r\nno name arguments are given, or if the -p option is supplied, a list of shell builtins is printed. With no other\r\noption arguments, the list consists of all enabled shell builtins. If -n is supplied, only disabled builtins are\r\nprinted. If -a is supplied, the list printed includes all builtins, with an indication of whether or not each is\r\nenabled. If -s is supplied, the output is restricted to the POSIX special builtins. The return value is 0 unless\r\na name is not a shell builtin or there is an error loading a new builtin from a shared object.\r\neval [arg ...]\r\nThe args are read and concatenated together into a single command. This command is then read and\r\nexecuted by the shell, and its exit status is returned as the value of eval. If there are no args, or only null\r\narguments, eval returns 0.\r\nexec [-cl] [-a name] [command [arguments]]\r\nIf command is specified, it replaces the shell. No new process is created. The arguments become the\r\narguments to command. If the -l option is supplied, the shell places a dash at the beginning of the zeroth\r\nargument passed to command. This is what login(1) does. The -c option causes command to be executed\r\nwith an empty environment. If -a is supplied, the shell passes name as the zeroth argument to the executed\r\ncommand. If command cannot be executed for some reason, a non-interactive shell exits, unless the shell\r\noption execfail is enabled, in which case it returns failure. An interactive shell returns failure if the file\r\ncannot be executed. If command is not specified, any redirections take effect in the current shell, and the\r\nreturn status is 0. If there is a redirection error, the return status is 1.\r\nexit [n]\r\nhttps://linux.die.net/man/1/bash\r\nPage 81 of 107\n\nCause the shell to exit with a status of n. If n is omitted, the exit status is that of the last command\r\nexecuted. A trap on EXIT is executed before the shell terminates.\r\nexport [-fn] [name[=word]] ...\r\nexport -p\r\nThe supplied names are marked for automatic export to the environment of subsequently executed\r\ncommands. If the -f option is given, the names refer to functions. If no names are given, or if the -p option\r\nis supplied, a list of all names that are exported in this shell is printed. The -n option causes the export\r\nproperty to be removed from each name. If a variable name is followed by =word, the value of the variable\r\nis set to word. export returns an exit status of 0 unless an invalid option is encountered, one of the names is\r\nnot a valid shell variable name, or -f is supplied with a name that is not a function.\r\nfc [-e ename] [-lnr] [first] [last]\r\nfc -s [pat=rep] [cmd]\r\nFix Command. In the first form, a range of commands from first to last is selected from the history list.\r\nFirst and last may be specified as a string (to locate the last command beginning with that string) or as a\r\nnumber (an index into the history list, where a negative number is used as an offset from the current\r\ncommand number). If last is not specified it is set to the current command for listing (so that ''fc -l -10''\r\nprints the last 10 commands) and to first otherwise. If first is not specified it is set to the previous\r\ncommand for editing and -16 for listing.\r\nThe -n option suppresses the command numbers when listing. The -r option reverses the order of the\r\ncommands. If the -l option is given, the commands are listed on standard output. Otherwise, the editor\r\ngiven by ename is invoked on a file containing those commands. If ename is not given, the value of the\r\nFCEDIT variable is used, and the value of EDITOR if FCEDIT is not set. If neither variable is set, vi is used.\r\nWhen editing is complete, the edited commands are echoed and executed.\r\nIn the second form, command is re-executed after each instance of pat is replaced by rep. A useful alias to\r\nuse with this is ''r=\"fc -s\"'', so that typing ''r cc'' runs the last command beginning with ''cc'' and typing ''r''\r\nre-executes the last command.\r\nIf the first form is used, the return value is 0 unless an invalid option is encountered or first or last specify\r\nhistory lines out of range. If the -e option is supplied, the return value is the value of the last command\r\nexecuted or failure if an error occurs with the temporary file of commands. If the second form is used, the\r\nreturn status is that of the command re-executed, unless cmd does not specify a valid history line, in which\r\ncase fc returns failure.\r\nfg [jobspec]\r\nResume jobspec in the foreground, and make it the current job. If jobspec is not present, the shell's notion\r\nof the current job is used. The return value is that of the command placed into the foreground, or failure if\r\nrun when job control is disabled or, when run with job control enabled, if jobspec does not specify a valid\r\njob or jobspec specifies a job that was started without job control.\r\ngetopts optstring name [args]\r\ngetopts is used by shell procedures to parse positional parameters. optstring contains the option characters\r\nto be recognized; if a character is followed by a colon, the option is expected to have an argument, which\r\nshould be separated from it by white space. The colon and question mark characters may not be used as\r\nhttps://linux.die.net/man/1/bash\r\nPage 82 of 107\n\noption characters. Each time it is invoked, getopts places the next option in the shell variable name,\r\ninitializing name if it does not exist, and the index of the next argument to be processed into the variable\r\nOPTIND. OPTIND is initialized to 1 each time the shell or a shell script is invoked. When an option requires\r\nan argument, getopts places that argument into the variable OPTARG. The shell does not reset OPTIND\r\nautomatically; it must be manually reset between multiple calls to getopts within the same shell invocation\r\nif a new set of parameters is to be used.\r\nWhen the end of options is encountered, getopts exits with a return value greater than zero. OPTIND is set\r\nto the index of the first non-option argument, and name is set to ?.\r\ngetopts normally parses the positional parameters, but if more arguments are given in args, getopts parses\r\nthose instead.\r\ngetopts can report errors in two ways. If the first character of optstring is a colon, silent error reporting is\r\nused. In normal operation diagnostic messages are printed when invalid options or missing option\r\narguments are encountered. If the variable OPTERR is set to 0, no error messages will be displayed, even if\r\nthe first character of optstring is not a colon.\r\nIf an invalid option is seen, getopts places ? into name and, if not silent, prints an error message and unsets\r\nOPTARG. If getopts is silent, the option character found is placed in OPTARG and no diagnostic message is\r\nprinted.\r\nIf a required argument is not found, and getopts is not silent, a question mark (?) is placed in name,\r\nOPTARG is unset, and a diagnostic message is printed. If getopts is silent, then a colon (:) is placed in\r\nname and OPTARG is set to the option character found.\r\ngetopts returns true if an option, specified or unspecified, is found. It returns false if the end of options is\r\nencountered or an error occurs.\r\nhash [-lr] [-p filename] [-dt] [name]\r\nFor each name, the full file name of the command is determined by searching the directories in $PATH and\r\nremembered. If the -p option is supplied, no path search is performed, and filename is used as the full file\r\nname of the command. The -r option causes the shell to forget all remembered locations. The -d option\r\ncauses the shell to forget the remembered location of each name. If the -t option is supplied, the full\r\npathname to which each name corresponds is printed. If multiple name arguments are supplied with -t, the\r\nname is printed before the hashed full pathname. The -l option causes output to be displayed in a format\r\nthat may be reused as input. If no arguments are given, or if only -l is supplied, information about\r\nremembered commands is printed. The return status is true unless a name is not found or an invalid option\r\nis supplied.\r\nhelp [-dms] [pattern]\r\nDisplay helpful information about builtin commands. If pattern is specified, help gives detailed help on all\r\ncommands matching pattern; otherwise help for all the builtins and shell control structures is printed.\r\n-d\r\nDisplay a short description of each pattern\r\nhttps://linux.die.net/man/1/bash\r\nPage 83 of 107\n\n-m\r\nDisplay the description of each pattern in a manpage-like format\r\n-s\r\nDisplay only a short usage synopsis for each pattern\r\nThe return status is 0 unless no command matches pattern.\r\nhistory [n]\r\nhistory -c\r\nhistory -d offset\r\nhistory -anrw [filename]\r\nhistory -p arg [arg ...]\r\nhistory -s arg [arg ...]\r\nWith no options, display the command history list with line numbers. Lines listed with a * have been\r\nmodified. An argument of n lists only the last n lines. If the shell variable HISTTIMEFORMAT is set and not\r\nnull, it is used as a format string for strftime(3) to display the time stamp associated with each displayed\r\nhistory entry. No intervening blank is printed between the formatted time stamp and the history line. If\r\nfilename is supplied, it is used as the name of the history file; if not, the value of HISTFILE is used.\r\nOptions, if supplied, have the following meanings:\r\n-c\r\nClear the history list by deleting all the entries.\r\n-d offset\r\nDelete the history entry at position offset.\r\n-a\r\nAppend the ''new'' history lines (history lines entered since the beginning of the current bash session) to the\r\nhistory file.\r\n-n\r\nRead the history lines not already read from the history file into the current history list. These are lines\r\nappended to the history file since the beginning of the current bash session.\r\n-r\r\nRead the contents of the history file and use them as the current history.\r\n-w\r\nWrite the current history to the history file, overwriting the history file's contents.\r\n-p\r\nhttps://linux.die.net/man/1/bash\r\nPage 84 of 107\n\nPerform history substitution on the following args and display the result on the standard output. Does not\r\nstore the results in the history list. Each arg must be quoted to disable normal history expansion.\r\n-s\r\nStore the args in the history list as a single entry. The last command in the history list is removed before the\r\nargs are added.\r\nIf the HISTTIMEFORMAT variable is set, the time stamp information associated with each history entry is\r\nwritten to the history file, marked with the history comment character. When the history file is read, lines\r\nbeginning with the history comment character followed immediately by a digit are interpreted as\r\ntimestamps for the previous history line. The return value is 0 unless an invalid option is encountered, an\r\nerror occurs while reading or writing the history file, an invalid offset is supplied as an argument to -d, or\r\nthe history expansion supplied as an argument to -p fails.\r\njobs [-lnprs] [ jobspec ... ]\r\njobs -x command [ args ... ]\r\nThe first form lists the active jobs. The options have the following meanings:\r\n-l\r\nList process IDs in addition to the normal information.\r\n-p\r\nList only the process ID of the job's process group leader.\r\n-n\r\nDisplay information only about jobs that have changed status since the user was last notified of their status.\r\n-r\r\nRestrict output to running jobs.\r\n-s\r\nRestrict output to stopped jobs.\r\nIf jobspec is given, output is restricted to information about that job. The return status is 0 unless an invalid\r\noption is encountered or an invalid jobspec is supplied.\r\nIf the -x option is supplied, jobs replaces any jobspec found in command or args with the corresponding\r\nprocess group ID, and executes command passing it args, returning its exit status.\r\nkill [-s sigspec | -n signum | -sigspec] [pid | jobspec] ...\r\nkill -l [sigspec | exit_status]\r\nSend the signal named by sigspec or signum to the processes named by pid or jobspec. sigspec is either a\r\ncase-insensitive signal name such as SIGKILL (with or without the SIG prefix) or a signal number; signum\r\nis a signal number. If sigspec is not present, then SIGTERM is assumed. An argument of -l lists the signal\r\nhttps://linux.die.net/man/1/bash\r\nPage 85 of 107\n\nnames. If any arguments are supplied when -l is given, the names of the signals corresponding to the\r\narguments are listed, and the return status is 0. The exit_status argument to -l is a number specifying either\r\na signal number or the exit status of a process terminated by a signal. kill returns true if at least one signal\r\nwas successfully sent, or false if an error occurs or an invalid option is encountered.\r\nlet arg [arg ...]\r\nEach arg is an arithmetic expression to be evaluated (see ARITHMETIC EVALUATION above). If the last arg\r\nevaluates to 0, let returns 1; 0 is returned otherwise.\r\nlocal [option] [name[=value] ...]\r\nFor each argument, a local variable named name is created, and assigned value. The option can be any of\r\nthe options accepted by declare. When local is used within a function, it causes the variable name to have\r\na visible scope restricted to that function and its children. With no operands, local writes a list of local\r\nvariables to the standard output. It is an error to use local when not within a function. The return status is 0\r\nunless local is used outside a function, an invalid name is supplied, or name is a readonly variable.\r\nlogout\r\nExit a login shell.\r\nmapfile [-n count] [-O origin] [-s count] [-t] [-u fd] [-C callback] [-c quantum] [array]\r\nreadarray [-n count] [-O origin] [-s count] [-t] [-u fd] [-C callback] [-c quantum] [array]\r\nRead lines from the standard input into the indexed array variable array, or from file descriptor fd if the -u\r\noption is supplied. The variable MAPFILE is the default array. Options, if supplied, have the following\r\nmeanings:\r\n-n\r\nCopy at most count lines. If count is 0, all lines are copied.\r\n-O\r\nBegin assigning to array at index origin. The default index is 0.\r\n-s\r\nDiscard the first count lines read.\r\n-t\r\nRemove a trailing newline from each line read.\r\n-u\r\nRead lines from file descriptor fd instead of the standard input.\r\n-C\r\nEvaluate callback each time quantum lines are read. The -c option specifies quantum.\r\n-c\r\nhttps://linux.die.net/man/1/bash\r\nPage 86 of 107\n\nSpecify the number of lines read between each call to callback.\r\nIf -C is specified without -c, the default quantum is 5000. When callback is evaluated, it is supplied the\r\nindex of the next array element to be assigned as an additional argument. callback is evaluated after the\r\nline is read but before the array element is assigned.\r\nIf not supplied with an explicit origin, mapfile will clear array before assigning to it.\r\nmapfile returns successfully unless an invalid option or option argument is supplied, array is invalid or\r\nunassignable, or if array is not an indexed array.\r\npopd [-n] [+n] [-n]\r\nRemoves entries from the directory stack. With no arguments, removes the top directory from the stack,\r\nand performs a cd to the new top directory. Arguments, if supplied, have the following meanings:\r\n-n\r\nSuppresses the normal change of directory when removing directories from the stack, so that only the stack\r\nis manipulated.\r\n+n\r\nRemoves the nth entry counting from the left of the list shown by dirs, starting with zero. For example:\r\n''popd +0'' removes the first directory, ''popd +1'' the second.\r\n-n\r\nRemoves the nth entry counting from the right of the list shown by dirs, starting with zero. For example:\r\n''popd -0'' removes the last directory, ''popd -1'' the next to last.\r\nIf the popd command is successful, a dirs is performed as well, and the return status is 0. popd returns\r\nfalse if an invalid option is encountered, the directory stack is empty, a non-existent directory stack entry is\r\nspecified, or the directory change fails.\r\nprintf [-v var] format [arguments]\r\nWrite the formatted arguments to the standard output under the control of the format. The format is a\r\ncharacter string which contains three types of objects: plain characters, which are simply copied to standard\r\noutput, character escape sequences, which are converted and copied to the standard output, and format\r\nspecifications, each of which causes printing of the next successive argument. In addition to the standard\r\nprintf(1) formats, %b causes printf to expand backslash escape sequences in the corresponding argument\r\n(except that \\c terminates output, backslashes in \\', \\\", and \\? are not removed, and octal escapes beginning\r\nwith \\0 may contain up to four digits), and %q causes printf to output the corresponding argument in a\r\nformat that can be reused as shell input.\r\nThe -v option causes the output to be assigned to the variable var rather than being printed to the standard\r\noutput.\r\nThe format is reused as necessary to consume all of the arguments. If the format requires more arguments\r\nthan are supplied, the extra format specifications behave as if a zero value or null string, as appropriate, had\r\nhttps://linux.die.net/man/1/bash\r\nPage 87 of 107\n\nbeen supplied. The return value is zero on success, non-zero on failure.\r\npushd [-n] [+n] [-n]\r\npushd [-n] [dir]\r\nAdds a directory to the top of the directory stack, or rotates the stack, making the new top of the stack the\r\ncurrent working directory. With no arguments, exchanges the top two directories and returns 0, unless the\r\ndirectory stack is empty. Arguments, if supplied, have the following meanings:\r\n-n\r\nSuppresses the normal change of directory when adding directories to the stack, so that only the stack is\r\nmanipulated.\r\n+n\r\nRotates the stack so that the nth directory (counting from the left of the list shown by dirs, starting with\r\nzero) is at the top.\r\n-n\r\nRotates the stack so that the nth directory (counting from the right of the list shown by dirs, starting with\r\nzero) is at the top.\r\ndir\r\nAdds dir to the directory stack at the top, making it the new current working directory.\r\nIf the pushd command is successful, a dirs is performed as well. If the first form is used, pushd returns 0\r\nunless the cd to dir fails. With the second form, pushd returns 0 unless the directory stack is empty, a non-existent directory stack element is specified, or the directory change to the specified new current directory\r\nfails.\r\npwd [-LP]\r\nPrint the absolute pathname of the current working directory. The pathname printed contains no symbolic\r\nlinks if the -P option is supplied or the -o physical option to the set builtin command is enabled. If the -L\r\noption is used, the pathname printed may contain symbolic links. The return status is 0 unless an error\r\noccurs while reading the name of the current directory or an invalid option is supplied.\r\nread [-ers] [-a aname] [-d delim] [-i text] [-n nchars] [-N nchars] [-p prompt] [-t timeout] [-u fd] [name ...]\r\nOne line is read from the standard input, or from the file descriptor fd supplied as an argument to the -u\r\noption, and the first word is assigned to the first name, the second word to the second name, and so on,\r\nwith leftover words and their intervening separators assigned to the last name. If there are fewer words read\r\nfrom the input stream than names, the remaining names are assigned empty values. The characters in IFS\r\nare used to split the line into words. The backslash character (\\) may be used to remove any special\r\nmeaning for the next character read and for line continuation. Options, if supplied, have the following\r\nmeanings:\r\n-a aname\r\nhttps://linux.die.net/man/1/bash\r\nPage 88 of 107\n\nThe words are assigned to sequential indices of the array variable aname, starting at 0. aname is unset before any\r\nnew values are assigned. Other name arguments are ignored.\r\n-d delim\r\nThe first character of delim is used to terminate the input line, rather than newline.\r\n-e\r\nIf the standard input is coming from a terminal, readline (see READLINE above) is used to obtain the line.\r\nReadline uses the current (or default, if line editing was not previously active) editing settings.\r\n-i text\r\nIf readline is being used to read the line, text is placed into the editing buffer before editing begins.\r\n-n nchars\r\nread returns after reading nchars characters rather than waiting for a complete line of input, but honor a delimiter\r\nif fewer than nchars characters are read before the delimiter.\r\n-N nchars\r\nread returns after reading exactly nchars characters rather than waiting for a complete line of input, unless EOF is\r\nencountered or read times out. Delimiter characters encountered in the input are not treated specially and do not\r\ncause read to return until nchars characters are read.\r\n-p prompt\r\nDisplay prompt on standard error, without a trailing newline, before attempting to read any input. The prompt is\r\ndisplayed only if input is coming from a terminal.\r\n-r\r\nBackslash does not act as an escape character. The backslash is considered to be part of the line. In\r\nparticular, a backslash-newline pair may not be used as a line continuation.\r\n-s\r\nSilent mode. If input is coming from a terminal, characters are not echoed.\r\n-t timeout\r\nCause read to time out and return failure if a complete line of input is not read within timeout seconds. timeout\r\nmay be a decimal number with a fractional portion following the decimal point. This option is only effective if\r\nread is reading input from a terminal, pipe, or other special file; it has no effect when reading from regular files. If\r\ntimeout is 0, read returns success if input is available on the specified file descriptor, failure otherwise. The exit\r\nstatus is greater than 128 if the timeout is exceeded.\r\nhttps://linux.die.net/man/1/bash\r\nPage 89 of 107\n\n-u fd\r\nRead input from file descriptor fd.\r\nIf no names are supplied, the line read is assigned to the variable REPLY. The return code is zero, unless\r\nend-of-file is encountered, read times out (in which case the return code is greater than 128), or an invalid\r\nfile descriptor is supplied as the argument to -u.\r\nreadonly [-aApf] [name[=word] ...]\r\nThe given names are marked readonly; the values of these names may not be changed by subsequent\r\nassignment. If the -f option is supplied, the functions corresponding to the names are so marked. The -a\r\noption restricts the variables to indexed arrays; the -A option restricts the variables to associative arrays. If\r\nno name arguments are given, or if the -p option is supplied, a list of all readonly names is printed. The -p\r\noption causes output to be displayed in a format that may be reused as input. If a variable name is followed\r\nby =word, the value of the variable is set to word. The return status is 0 unless an invalid option is\r\nencountered, one of the names is not a valid shell variable name, or -f is supplied with a name that is not a\r\nfunction.\r\nreturn [n]\r\nCauses a function to exit with the return value specified by n. If n is omitted, the return status is that of the\r\nlast command executed in the function body. If used outside a function, but during execution of a script by\r\nthe . (source) command, it causes the shell to stop executing that script and return either n or the exit status\r\nof the last command executed within the script as the exit status of the script. If used outside a function and\r\nnot during execution of a script by ., the return status is false. Any command associated with the RETURN\r\ntrap is executed before execution resumes after the function or script.\r\nset [--abefhkmnptuvxBCEHPT] [-o option] [arg ...]\r\nset [+abefhkmnptuvxBCEHPT] [+o option] [arg ...]\r\nWithout options, the name and value of each shell variable are displayed in a format that can be reused as\r\ninput for setting or resetting the currently-set variables. Read-only variables cannot be reset. In posix mode,\r\nonly shell variables are listed. The output is sorted according to the current locale. When options are\r\nspecified, they set or unset shell attributes. Any arguments remaining after option processing are treated as\r\nvalues for the positional parameters and are assigned, in order, to $1, $2, ... $n. Options, if specified, have\r\nthe following meanings:\r\n-a\r\nAutomatically mark variables and functions which are modified or created for export to the environment of\r\nsubsequent commands.\r\n-b\r\nReport the status of terminated background jobs immediately, rather than before the next primary prompt.\r\nThis is effective only when job control is enabled.\r\n-e\r\nExit immediately if a pipeline (which may consist of a single simple command), a subshell command\r\nenclosed in parentheses, or one of the commands executed as part of a command list enclosed by braces\r\nhttps://linux.die.net/man/1/bash\r\nPage 90 of 107\n\n(see SHELL GRAMMAR above) exits with a non-zero status. The shell does not exit if the command that\r\nfails is part of the command list immediately following a while or until keyword, part of the test following\r\nthe if or elif reserved words, part of any command executed in a \u0026\u0026 or ││ list except the command\r\nfollowing the final \u0026\u0026 or ││, any command in a pipeline but the last, or if the command's return value is\r\nbeing inverted with !. A trap on ERR, if set, is executed before the shell exits. This option applies to the\r\nshell environment and each subshell environment separately (see COMMAND EXECUTION ENVIRONMENT\r\nabove), and may cause subshells to exit before executing all the commands in the subshell.\r\n-f\r\nDisable pathname expansion.\r\n-h\r\nRemember the location of commands as they are looked up for execution. This is enabled by default.\r\n-k\r\nAll arguments in the form of assignment statements are placed in the environment for a command, not just\r\nthose that precede the command name.\r\n-m\r\nMonitor mode. Job control is enabled. This option is on by default for interactive shells on systems that\r\nsupport it (see JOB CONTROL above). Background processes run in a separate process group and a line\r\ncontaining their exit status is printed upon their completion.\r\n-n\r\nRead commands but do not execute them. This may be used to check a shell script for syntax errors. This is\r\nignored by interactive shells.\r\n-o option-name\r\nThe option-name can be one of the following:\r\nallexport\r\nSame as -a.\r\nbraceexpand\r\nSame as -B.\r\nemacs\r\nUse an emacs-style command line editing interface. This is enabled by default when the shell is interactive, unless\r\nthe shell is started with the --noediting option. This also affects the editing interface used for read -e.\r\nhttps://linux.die.net/man/1/bash\r\nPage 91 of 107\n\nerrexit\r\nSame as -e.\r\nerrtrace\r\nSame as -E.\r\nfunctrace\r\nSame as -T.\r\nhashall\r\nSame as -h.\r\nhistexpand\r\nSame as -H.\r\nhistory\r\nEnable command history, as described above under HISTORY. This option is on by default in interactive shells.\r\nignoreeof\r\nThe effect is as if the shell command ''IGNOREEOF=10'' had been executed (see Shell Variables above).\r\nkeyword\r\nSame as -k.\r\nmonitor\r\nSame as -m.\r\nnoclobber\r\nSame as -C.\r\nnoexec\r\nSame as -n.\r\nnoglob\r\nSame as -f.\r\nnolog\r\nCurrently ignored.\r\nhttps://linux.die.net/man/1/bash\r\nPage 92 of 107\n\nnotify\r\nSame as -b.\r\nnounset\r\nSame as -u.\r\nonecmd\r\nSame as -t.\r\nphysical\r\nSame as -P.\r\npipefail\r\nIf set, the return value of a pipeline is the value of the last (rightmost) command to exit with a non-zero status, or\r\nzero if all commands in the pipeline exit successfully. This option is disabled by default.\r\nposix\r\nChange the behavior of bash where the default operation differs from the POSIX standard to match the standard\r\n(posix mode).\r\nprivileged\r\nSame as -p.\r\nverbose\r\nSame as -v.\r\nvi\r\nUse a vi-style command line editing interface. This also affects the editing interface used for read -e.\r\nxtrace\r\nSame as -x.\r\nIf -o is supplied with no option-name, the values of the current options are printed. If +o is supplied with no\r\noption-name, a series of set commands to recreate the current option settings is displayed on the standard output.\r\n-p\r\nTurn on privileged mode. In this mode, the $ENV and $BASH_ENV files are not processed, shell functions\r\nare not inherited from the environment, and the SHELLOPTS, BASHOPTS, CDPATH, and GLOBIGNORE\r\nvariables, if they appear in the environment, are ignored. If the shell is started with the effective user\r\nhttps://linux.die.net/man/1/bash\r\nPage 93 of 107\n\n(group) id not equal to the real user (group) id, and the -p option is not supplied, these actions are taken\r\nand the effective user id is set to the real user id. If the -p option is supplied at startup, the effective user id\r\nis not reset. Turning this option off causes the effective user and group ids to be set to the real user and\r\ngroup ids.\r\n-t\r\nExit after reading and executing one command.\r\n-u\r\nTreat unset variables and parameters other than the special parameters \"@\" and \"*\" as an error when\r\nperforming parameter expansion. If expansion is attempted on an unset variable or parameter, the shell\r\nprints an error message, and, if not interactive, exits with a non-zero status.\r\n-v\r\nPrint shell input lines as they are read.\r\n-x\r\nAfter expanding each simple command, for command, case command, select command, or arithmetic for\r\ncommand, display the expanded value of PS4, followed by the command and its expanded arguments or\r\nassociated word list.\r\n-B\r\nThe shell performs brace expansion (see Brace Expansion above). This is on by default.\r\n-C\r\nIf set, bash does not overwrite an existing file with the \u003e, \u003e\u0026, and \u003c\u003e redirection operators. This may be\r\noverridden when creating output files by using the redirection operator \u003e| instead of \u003e.\r\n-E\r\nIf set, any trap on ERR is inherited by shell functions, command substitutions, and commands executed in\r\na subshell environment. The ERR trap is normally not inherited in such cases.\r\n-H\r\nEnable ! style history substitution. This option is on by default when the shell is interactive.\r\n-P\r\nIf set, the shell does not follow symbolic links when executing commands such as cd that change the\r\ncurrent working directory. It uses the physical directory structure instead. By default, bash follows the\r\nlogical chain of directories when performing commands which change the current directory.\r\nhttps://linux.die.net/man/1/bash\r\nPage 94 of 107\n\n-T\r\nIf set, any traps on DEBUG and RETURN are inherited by shell functions, command substitutions, and\r\ncommands executed in a subshell environment. The DEBUG and RETURN traps are normally not\r\ninherited in such cases.\r\n--\r\nIf no arguments follow this option, then the positional parameters are unset. Otherwise, the positional\r\nparameters are set to the args, even if some of them begin with a -.\r\n-\r\nSignal the end of options, cause all remaining args to be assigned to the positional parameters. The -x and -\r\nv options are turned off. If there are no args, the positional parameters remain unchanged.\r\nThe options are off by default unless otherwise noted. Using + rather than - causes these options to be\r\nturned off. The options can also be specified as arguments to an invocation of the shell. The current set of\r\noptions may be found in $-. The return status is always true unless an invalid option is encountered.\r\nshift [n]\r\nThe positional parameters from n+1 ... are renamed to $1 .... Parameters represented by the numbers $#\r\ndown to $#-n+1 are unset. n must be a non-negative number less than or equal to $#. If n is 0, no\r\nparameters are changed. If n is not given, it is assumed to be 1. If n is greater than $#, the positional\r\nparameters are not changed. The return status is greater than zero if n is greater than $# or less than zero;\r\notherwise 0.\r\nshopt [-pqsu] [-o] [optname ...]\r\nToggle the values of variables controlling optional shell behavior. With no options, or with the -p option, a\r\nlist of all settable options is displayed, with an indication of whether or not each is set. The -p option\r\ncauses output to be displayed in a form that may be reused as input. Other options have the following\r\nmeanings:\r\n-s\r\nEnable (set) each optname.\r\n-u\r\nDisable (unset) each optname.\r\n-q\r\nSuppresses normal output (quiet mode); the return status indicates whether the optname is set or unset. If\r\nmultiple optname arguments are given with -q, the return status is zero if all optnames are enabled; non-zero otherwise.\r\n-o\r\nRestricts the values of optname to be those defined for the -o option to the set builtin.\r\nhttps://linux.die.net/man/1/bash\r\nPage 95 of 107\n\nIf either -s or -u is used with no optname arguments, the display is limited to those options which are set or\r\nunset, respectively. Unless otherwise noted, the shopt options are disabled (unset) by default.\r\nThe return status when listing options is zero if all optnames are enabled, non-zero otherwise. When setting\r\nor unsetting options, the return status is zero unless an optname is not a valid shell option.\r\nThe list of shopt options is:\r\nautocd\r\nIf set, a command name that is the name of a directory is executed as if it were the argument to the cd\r\ncommand. This option is only used by interactive shells.\r\ncdable_vars\r\nIf set, an argument to the cd builtin command that is not a directory is assumed to be the name of a variable whose\r\nvalue is the directory to change to.\r\ncdspell\r\nIf set, minor errors in the spelling of a directory component in a cd command will be corrected. The errors\r\nchecked for are transposed characters, a missing character, and one character too many. If a correction is\r\nfound, the corrected file name is printed, and the command proceeds. This option is only used by\r\ninteractive shells.\r\ncheckhash\r\nIf set, bash checks that a command found in the hash table exists before trying to execute it. If a hashed command\r\nno longer exists, a normal path search is performed.\r\ncheckjobs\r\nIf set, bash lists the status of any stopped and running jobs before exiting an interactive shell. If any jobs are\r\nrunning, this causes the exit to be deferred until a second exit is attempted without an intervening command (see\r\nJOB CONTROL above). The shell always postpones exiting if any jobs are stopped.\r\ncheckwinsize\r\nIf set, bash checks the window size after each command and, if necessary, updates the values of LINES and\r\nCOLUMNS.\r\ncmdhist\r\nIf set, bash attempts to save all lines of a multiple-line command in the same history entry. This allows\r\neasy re-editing of multi-line commands.\r\ncompat31\r\nhttps://linux.die.net/man/1/bash\r\nPage 96 of 107\n\nIf set, bash changes its behavior to that of version 3.1 with respect to quoted arguments to the conditional\r\ncommand's =~ operator.\r\ncompat32\r\nIf set, bash changes its behavior to that of version 3.2 with respect to locale-specific string comparison when\r\nusing the conditional command's \u003c and \u003e operators.\r\ncompat40\r\nIf set, bash changes its behavior to that of version 4.0 with respect to locale-specific string comparison when\r\nusing the conditional command's \u003c and \u003e operators and the effect of interrupting a command list.\r\ndirspell\r\nIf set, bash attempts spelling correction on directory names during word completion if the directory name initially\r\nsupplied does not exist.\r\ndotglob\r\nIf set, bash includes filenames beginning with a '.' in the results of pathname expansion.\r\nexecfail\r\nIf set, a non-interactive shell will not exit if it cannot execute the file specified as an argument to the exec builtin\r\ncommand. An interactive shell does not exit if exec fails.\r\nexpand_aliases\r\nIf set, aliases are expanded as described above under ALIASES. This option is enabled by default for interactive\r\nshells.\r\nextdebug\r\nIf set, behavior intended for use by debuggers is enabled:\r\n1.\r\nThe -F option to the declare builtin displays the source file name and line number corresponding to each\r\nfunction name supplied as an argument.\r\n2.\r\nIf the command run by the DEBUG trap returns a non-zero value, the next command is skipped and not\r\nexecuted.\r\n3.\r\nIf the command run by the DEBUG trap returns a value of 2, and the shell is executing in a subroutine (a\r\nshell function or a shell script executed by the . or source builtins), a call to return is simulated.\r\nhttps://linux.die.net/man/1/bash\r\nPage 97 of 107\n\n4.\r\nBASH_ARGC and BASH_ARGV are updated as described in their descriptions above.\r\n5.\r\nFunction tracing is enabled: command substitution, shell functions, and subshells invoked with ( command\r\n) inherit the DEBUG and RETURN traps.\r\n6.\r\nError tracing is enabled: command substitution, shell functions, and subshells invoked with ( command )\r\ninherit the ERROR trap.\r\nextglob\r\nIf set, the extended pattern matching features\r\ndescribed above under Pathname Expansion are enabled.\r\nextquote\r\nIf set, $'string' and $\"string\" quoting is performed within ${parameter} expansions enclosed in double quotes.\r\nThis option is enabled by default.\r\nfailglob\r\nIf set, patterns which fail to match filenames during pathname expansion result in an expansion error.\r\nforce_fignore\r\nIf set, the suffixes specified by the FIGNORE shell variable cause words to be ignored when performing word\r\ncompletion even if the ignored words are the only possible completions. See SHELL VARIABLES above for a\r\ndescription of FIGNORE. This option is enabled by default.\r\nglobstar\r\nIf set, the pattern ** used in a pathname expansion context will match a files and zero or more directories and\r\nsubdirectories. If the pattern is followed by a /, only directories and subdirectories match.\r\ngnu_errfmt\r\nIf set, shell error messages are written in the standard GNU error message format.\r\nhistappend\r\nIf set, the history list is appended to the file named by the value of the HISTFILE variable when the shell exits,\r\nrather than overwriting the file.\r\nhistreedit\r\nhttps://linux.die.net/man/1/bash\r\nPage 98 of 107\n\nIf set, and readline is being used, a user is given the opportunity to re-edit a failed history substitution.\r\nhistverify\r\nIf set, and readline is being used, the results of history substitution are not immediately passed to the shell parser.\r\nInstead, the resulting line is loaded into the readline editing buffer, allowing further modification.\r\nhostcomplete\r\nIf set, and readline is being used, bash will attempt to perform hostname completion when a word containing a @\r\nis being completed (see Completing under READLINE above). This is enabled by default.\r\nhuponexit\r\nIf set, bash will send SIGHUP to all jobs when an interactive login shell exits.\r\ninteractive_comments\r\nIf set, allow a word beginning with # to cause that word and all remaining characters on that line to be ignored in\r\nan interactive shell (see COMMENTS above). This option is enabled by default.\r\nlithist\r\nIf set, and the cmdhist option is enabled, multi-line commands are saved to the history with embedded\r\nnewlines rather than using semicolon separators where possible.\r\nlogin_shell\r\nThe shell sets this option if it is started as a login shell (see INVOCATION above). The value may not be changed.\r\nmailwarn\r\nIf set, and a file that bash is checking for mail has been accessed since the last time it was checked, the message\r\n''The mail in mailfile has been read'' is displayed.\r\nno_empty_cmd_completion\r\nIf set, and readline is being used, bash will not attempt to search the PATH for possible completions when\r\ncompletion is attempted on an empty line.\r\nnocaseglob\r\nIf set, bash matches filenames in a case-insensitive fashion when performing pathname expansion (see Pathname\r\nExpansion above).\r\nnocasematch\r\nIf set, bash matches patterns in a case-insensitive fashion when performing matching while executing case or [[\r\nconditional commands.\r\nhttps://linux.die.net/man/1/bash\r\nPage 99 of 107\n\nnullglob\r\nIf set, bash allows patterns which match no files (see Pathname Expansion above) to expand to a null string,\r\nrather than themselves.\r\nprogcomp\r\nIf set, the programmable completion facilities (see Programmable Completion above) are enabled. This option is\r\nenabled by default.\r\npromptvars\r\nIf set, prompt strings undergo parameter expansion, command substitution, arithmetic expansion, and quote\r\nremoval after being expanded as described in PROMPTING above. This option is enabled by default.\r\nrestricted_shell\r\nThe shell sets this option if it is started in restricted mode (see RESTRICTED SHELL below). The value may not be\r\nchanged. This is not reset when the startup files are executed, allowing the startup files to discover whether or not\r\na shell is restricted.\r\nshift_verbose\r\nIf set, the shift builtin prints an error message when the shift count exceeds the number of positional parameters.\r\nsourcepath\r\nIf set, the source (.) builtin uses the value of PATH to find the directory containing the file supplied as an\r\nargument. This option is enabled by default.\r\nxpg_echo\r\nIf set, the echo builtin expands backslash-escape sequences by default.\r\nsuspend [-f]\r\nSuspend the execution of this shell until it receives a SIGCONT signal. When the suspended shell is a\r\nbackground process, it can be restarted by the fg command. For more information, read the JOB CONTROL\r\nsection. The suspend command can not suspend the login shell. However, when -f option is specified,\r\nsuspend command can suspend even login shell. The return status is 0 unless the shell is a login shell and -\r\nf is not supplied, or if job control is not enabled.\r\ntest expr\r\n[ expr ]\r\nReturn a status of 0 or 1 depending on the evaluation of the conditional expression expr. Each operator and\r\noperand must be a separate argument. Expressions are composed of the primaries described above under\r\nCONDITIONAL EXPRESSIONS. test does not accept any options, nor does it accept and ignore an argument\r\nof -- as signifying the end of options.\r\nhttps://linux.die.net/man/1/bash\r\nPage 100 of 107\n\nExpressions may be combined using the following operators, listed in decreasing order of precedence. The\r\nevaluation depends on the number of arguments; see below.\r\n! expr\r\nTrue if expr is false.\r\n( expr )\r\nReturns the value of expr. This may be used to override the normal precedence of operators.\r\nexpr1 -a expr2\r\nTrue if both expr1 and expr2 are true.\r\nexpr1 -o expr2\r\nTrue if either expr1 or expr2 is true.\r\ntest and [ evaluate conditional expressions using a set of rules based on the number of arguments.\r\n0 arguments\r\nThe expression is false.\r\n1 argument\r\nThe expression is true if and only if the argument is not null.\r\n2 arguments\r\nIf the first argument is !, the expression is true if and only if the second argument is null. If the first argument is\r\none of the unary conditional operators listed above under CONDITIONAL EXPRESSIONS, the expression is true if\r\nthe unary test is true. If the first argument is not a valid unary conditional operator, the expression is false.\r\n3 arguments\r\nIf the second argument is one of the binary conditional operators listed above under CONDITIONAL EXPRESSIONS,\r\nthe result of the expression is the result of the binary test using the first and third arguments as operands. The -a\r\nand -o operators are considered binary operators when there are three arguments. If the first argument is !, the\r\nvalue is the negation of the two-argument test using the second and third arguments. If the first argument is\r\nexactly ( and the third argument is exactly ), the result is the one-argument test of the second argument. Otherwise,\r\nthe expression is false.\r\n4 arguments\r\nIf the first argument is !, the result is the negation of the three-argument expression composed of the remaining\r\narguments. Otherwise, the expression is parsed and evaluated according to precedence using the rules listed above.\r\n5 or more arguments\r\nhttps://linux.die.net/man/1/bash\r\nPage 101 of 107\n\nThe expression is parsed and evaluated according to precedence using the rules listed above.\r\ntimes\r\nPrint the accumulated user and system times for the shell and for processes run from the shell. The return status is\r\n0.\r\ntrap [-lp] [[arg] sigspec ...]\r\nThe command arg is to be read and executed when the shell receives signal(s) sigspec. If arg is absent (and\r\nthere is a single sigspec) or -, each specified signal is reset to its original disposition (the value it had upon\r\nentrance to the shell). If arg is the null string the signal specified by each sigspec is ignored by the shell\r\nand by the commands it invokes. If arg is not present and -p has been supplied, then the trap commands\r\nassociated with each sigspec are displayed. If no arguments are supplied or if only -p is given, trap prints\r\nthe list of commands associated with each signal. The -l option causes the shell to print a list of signal\r\nnames and their corresponding numbers. Each sigspec is either a signal name defined in \u003csignal.h\u003e, or a\r\nsignal number. Signal names are case insensitive and the SIG prefix is optional.\r\nIf a sigspec is EXIT (0) the command arg is executed on exit from the shell. If a sigspec is DEBUG, the\r\ncommand arg is executed before every simple command, for command, case command, select command,\r\nevery arithmetic for command, and before the first command executes in a shell function (see SHELL\r\nGRAMMAR above). Refer to the description of the extdebug option to the shopt builtin for details of its\r\neffect on the DEBUG trap. If a sigspec is RETURN, the command arg is executed each time a shell function\r\nor a script executed with the . or source builtins finishes executing.\r\nIf a sigspec is ERR, the command arg is executed whenever a simple command has a non-zero exit status,\r\nsubject to the following conditions. The ERR trap is not executed if the failed command is part of the\r\ncommand list immediately following a while or until keyword, part of the test in an if statement, part of a\r\ncommand executed in a \u0026\u0026 or ││ list, or if the command's return value is being inverted via !. These are\r\nthe same conditions obeyed by the errexit option.\r\nSignals ignored upon entry to the shell cannot be trapped, reset or listed. Trapped signals that are not being\r\nignored are reset to their original values in a subshell or subshell environment when one is created. The\r\nreturn status is false if any sigspec is invalid; otherwise trap returns true.\r\ntype [-aftpP] name [name ...]\r\nWith no options, indicate how each name would be interpreted if used as a command name. If the -t option\r\nis used, type prints a string which is one of alias, keyword, function, builtin, or file if name is an alias, shell\r\nreserved word, function, builtin, or disk file, respectively. If the name is not found, then nothing is printed,\r\nand an exit status of false is returned. If the -p option is used, type either returns the name of the disk file\r\nthat would be executed if name were specified as a command name, or nothing if ''type -t name'' would not\r\nreturn file. The -P option forces a PATH search for each name, even if ''type -t name'' would not return file.\r\nIf a command is hashed, -p and -P print the hashed value, not necessarily the file that appears first in PATH.\r\nIf the -a option is used, type prints all of the places that contain an executable named name. This includes\r\naliases and functions, if and only if the -p option is not also used. The table of hashed commands is not\r\nhttps://linux.die.net/man/1/bash\r\nPage 102 of 107\n\nconsulted when using -a. The -f option suppresses shell function lookup, as with the command builtin.\r\ntype returns true if all of the arguments are found, false if any are not found.\r\nulimit [-HSTabcdefilmnpqrstuvx [limit]]\r\nProvides control over the resources available to the shell and to processes started by it, on systems that\r\nallow such control. The -H and -S options specify that the hard or soft limit is set for the given resource. A\r\nhard limit cannot be increased by a non-root user once it is set; a soft limit may be increased up to the value\r\nof the hard limit. If neither -H nor -S is specified, both the soft and hard limits are set. The value of limit\r\ncan be a number in the unit specified for the resource or one of the special values hard, soft, or unlimited,\r\nwhich stand for the current hard limit, the current soft limit, and no limit, respectively. If limit is omitted,\r\nthe current value of the soft limit of the resource is printed, unless the -H option is given. When more than\r\none resource is specified, the limit name and unit are printed before the value. Other options are interpreted\r\nas follows:\r\n-a\r\nAll current limits are reported\r\n-b\r\nThe maximum socket buffer size\r\n-c\r\nThe maximum size of core files created\r\n-d\r\nThe maximum size of a process's data segment\r\n-e\r\nThe maximum scheduling priority (\"nice\")\r\n-f\r\nThe maximum size of files written by the shell and its children\r\n-i\r\nThe maximum number of pending signals\r\n-l\r\nThe maximum size that may be locked into memory\r\n-m\r\nThe maximum resident set size (many systems do not honor this limit)\r\n-n\r\nhttps://linux.die.net/man/1/bash\r\nPage 103 of 107\n\nThe maximum number of open file descriptors (most systems do not allow this value to be set)\r\n-p\r\nThe pipe size in 512-byte blocks (this may not be set)\r\n-q\r\nThe maximum number of bytes in POSIX message queues\r\n-r\r\nThe maximum real-time scheduling priority\r\n-s\r\nThe maximum stack size\r\n-t\r\nThe maximum amount of cpu time in seconds\r\n-u\r\nThe maximum number of processes available to a single user\r\n-v\r\nThe maximum amount of virtual memory available to the shell\r\n-x\r\nThe maximum number of file locks\r\n-T\r\nThe maximum number of threads\r\nIf limit is given, it is the new value of the specified resource (the -a option is display only). If no option is\r\ngiven, then -f is assumed. Values are in 1024-byte increments, except for -t, which is in seconds, -p, which\r\nis in units of 512-byte blocks, and -T, -b, -n, and -u, which are unscaled values. The return status is 0\r\nunless an invalid option or argument is supplied, or an error occurs while setting a new limit.\r\numask [-p] [-S] [mode]\r\nThe user file-creation mask is set to mode. If mode begins with a digit, it is interpreted as an octal number;\r\notherwise it is interpreted as a symbolic mode mask similar to that accepted by chmod(1). If mode is\r\nomitted, the current value of the mask is printed. The -S option causes the mask to be printed in symbolic\r\nform; the default output is an octal number. If the -p option is supplied, and mode is omitted, the output is\r\nin a form that may be reused as input. The return status is 0 if the mode was successfully changed or if no\r\nmode argument was supplied, and false otherwise.\r\nhttps://linux.die.net/man/1/bash\r\nPage 104 of 107\n\nunalias [-a] [name ...]\r\nRemove each name from the list of defined aliases. If -a is supplied, all alias definitions are removed. The\r\nreturn value is true unless a supplied name is not a defined alias.\r\nunset [-fv] [name ...]\r\nFor each name, remove the corresponding variable or function. If no options are supplied, or the -v option\r\nis given, each name refers to a shell variable. Read-only variables may not be unset. If -f is specified, each\r\nname refers to a shell function, and the function definition is removed. Each unset variable or function is\r\nremoved from the environment passed to subsequent commands. If any of COMP_WORDBREAKS,\r\nRANDOM, SECONDS, LINENO, HISTCMD, FUNCNAME, GROUPS, or DIRSTACK are unset, they lose their\r\nspecial properties, even if they are subsequently reset. The exit status is true unless a name is readonly.\r\nwait [n ...]\r\nWait for each specified process and return its termination status. Each n may be a process ID or a job\r\nspecification; if a job spec is given, all processes in that job's pipeline are waited for. If n is not given, all\r\ncurrently active child processes are waited for, and the return status is zero. If n specifies a non-existent\r\nprocess or job, the return status is 127. Otherwise, the return status is the exit status of the last process or\r\njob waited for.\r\nRestricted Shell\r\nIf bash is started with the name rbash, or the -r option is supplied at invocation, the shell becomes restricted. A\r\nrestricted shell is used to set up an environment more controlled than the standard shell. It behaves identically to\r\nbash with the exception that the following are disallowed or not performed:\r\n• changing directories with cd\r\n• setting or unsetting the values of SHELL, PATH, ENV, or BASH_ENV\r\n• specifying command names containing /\r\n• specifying a file name containing a / as an argument to the . builtin command\r\n• Specifying a filename containing a slash as an argument to the -p option to the hash builtin command\r\n• importing function definitions from the shell environment at startup\r\n• parsing the value of SHELLOPTS from the shell environment at startup\r\n• redirecting output using the \u003e, \u003e|, \u003c\u003e, \u003e\u0026, \u0026\u003e, and \u003e\u003e redirection operators\r\n• using the exec builtin command to replace the shell with another command\r\n• adding or deleting builtin commands with the -f and -d options to the enable builtin command\r\n• Using the enable builtin command to enable disabled shell builtins\r\n• specifying the -p option to the command builtin command\r\nhttps://linux.die.net/man/1/bash\r\nPage 105 of 107\n\n• turning off restricted mode with set +r or set +o restricted.\r\nThese restrictions are enforced after any startup files are read.\r\nWhen a command that is found to be a shell script is executed (see COMMAND EXECUTION above), rbash turns\r\noff any restrictions in the shell spawned to execute the script.\r\nSee Also\r\nBash Reference Manual, Brian Fox and Chet Ramey\r\nThe Gnu Readline Library, Brian Fox and Chet Ramey\r\nThe Gnu History Library, Brian Fox and Chet Ramey\r\nPortable Operating System Interface (POSIX) Part 2: Shell and Utilities, IEEE\r\nsh(1), ksh(1), csh(1)\r\nemacs(1), vi(1)\r\nreadline(3)\r\nFiles\r\n/bin/bash\r\nThe bash executable\r\n/etc/profile\r\nThe systemwide initialization file, executed for login shells\r\n/etc/bash.bash_logout\r\nThe systemwide login shell cleanup file, executed when a login shell exits\r\n~/.bash_profile\r\nThe personal initialization file, executed for login shells\r\n~/.bashrc\r\nThe individual per-interactive-shell startup file\r\n~/.bash_logout\r\nThe individual login shell cleanup file, executed when a login shell exits\r\n~/.inputrc\r\nIndividual readline initialization file\r\nAuthors\r\nBrian Fox, Free Software Foundation\r\nbfox@gnu.org\r\nChet Ramey, Case Western Reserve University\r\nchet.ramey@case.edu\r\nBug Reports\r\nhttps://linux.die.net/man/1/bash\r\nPage 106 of 107\n\nIf you find a bug in bash, you should report it. But first, you should make sure that it really is a bug, and that it\r\nappears in the latest version of bash. The latest version is always available from ftp://ftp.gnu.org/pub/bash/.\r\nOnce you have determined that a bug actually exists, use the bashbug command (from the source package) to\r\nsubmit a bug report. If you have a fix, you are encouraged to mail that as well! Suggestions and 'philosophical'\r\nbug reports may be mailed to bug-bash@gnu.org or posted to the Usenet newsgroup gnu.bash.bug.\r\nALL bug reports should include:\r\nThe version number of bash\r\nThe hardware and operating system\r\nThe compiler used to compile\r\nA description of the bug behaviour\r\nA short script or 'recipe' which exercises the bug\r\nComments and bug reports concerning this manual page should be directed to chet@po.cwru.edu.\r\nBugs\r\nIt's too big and too slow.\r\nThere are some subtle differences between bash and traditional versions of sh, mostly because of the POSIX\r\nspecification.\r\nAliases are confusing in some uses.\r\nShell builtin commands and functions are not stoppable/restartable.\r\nCompound commands and command sequences of the form 'a ; b ; c' are not handled gracefully when process\r\nsuspension is attempted. When a process is stopped, the shell immediately executes the next command in the\r\nsequence. It suffices to place the sequence of commands between parentheses to force it into a subshell, which\r\nmay be stopped as a unit.\r\nArray variables may not (yet) be exported.\r\nThere may be only one active coprocess at a time.\r\nReferenced By\r\na2x(1), bashbug(1), cdecl(1), cogito(7), core(5), credentials(7), cupsenable(8), environ(5), environ(7),\r\nfirehol(1), firehol.conf(5), getopt(1), getopt(3), gimprc(5), gimprc-2.0(5), gimprc-2.2(5),\r\ngmt_shell_functions(1), groffer(1), history(3), intro(1), kill(1), man2html(1), mc(1), pass(1), pmdabash(1),\r\nproc(5), read(1), setpgrp(2), svgalib(7), tcflush(3), terminal(1), time(1), tpipe(1), ulimit(3), vgseer(1),\r\nviewglob(1), virt-rescue(1), wcd(1), which(1), zoiduser(1), zsh(1), zshall(1)\r\nSource: https://linux.die.net/man/1/bash\r\nhttps://linux.die.net/man/1/bash\r\nPage 107 of 107",
	"extraction_quality": 1,
	"language": "EN",
	"sources": [
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	"references": [
		"https://linux.die.net/man/1/bash"
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