Bash - ArchWiki
Archived: 2026-04-05 20:20:35 UTC
Bash (Bourne-Again SHell) is a command-line shell/programming language by the GNU Project. Its name alludes
to its predecessor, the long-deprecated Bourne shell. Bash can be run on most Unix-like operating systems,
including GNU/Linux.
Bash is the default command-line shell on Arch Linux.
Invocation
Bash behaviour can be altered depending on how it is invoked. Some descriptions of different modes follow.
If Bash is spawned by login in a TTY, by an SSH daemon, or similar means, it is considered a login shell. This
mode can also be engaged using the -l / --login command line option.
Bash is considered an interactive shell when its standard input, output and error are connected to a terminal (for
example, when run in a terminal emulator), and it is not started with the -c option or non-option arguments (for
example, bash script ). All interactive shells source /etc/bash.bashrc and ~/.bashrc , while interactive
login shells also source /etc/profile and ~/.bash_profile .
Note In Arch /bin/sh (which used to be the Bourne shell executable) is symlinked to bash . If Bash is invoked
with the name sh , it tries to mimic the startup behavior of historical versions of sh , including POSIX
compatibility.
Configuration files
Bash will attempt to execute a set of startup files depending on how it was invoked. See the Bash Startup Files
section of the GNU Bash manual for a complete description.
File Description
Login
shells
(see
note)
Interactive,
non-login
shells
/etc/profile
Sources application settings in
/etc/profile.d/*.sh and /etc/bash.bashrc .
Yes No
~/.bash_profile
Per-user, after /etc/profile . If this file does not
exist, ~/.bash_login and ~/.profile are checked
in that order. The skeleton file
/etc/skel/.bash_profile also sources
~/.bashrc .
Yes No
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~/.bash_logout Per-user, after exit of a login shell. Yes No
/etc/bash.bash_logout
Depends on the -
DSYS_BASH_LOGOUT="/etc/bash.bash_logout"
compilation flag. After exit of a login shell.
Yes No
/etc/bash.bashrc
Depends on the -DSYS_BASHRC="/etc/bash.bashrc"
compilation flag. Sources /usr/share/bash-completion/bash_completion .No Yes
~/.bashrc Per-user, after /etc/bash.bashrc . No Yes
Note
Login shells can be non-interactive when called with the --login argument.
While interactive, non-login shells do not source ~/.bash_profile , they still inherit the environment
from their parent process (which may be a login shell). See GregsWiki:ProcessManagement#On processes,
environments and inheritance for details.
Shell and environment variables
The behavior of Bash and programs run by it can be influenced by a number of environment variables.
Environment variables are used to store useful values such as command search directories, or which browser to
use. When a new shell or script is launched it inherits its parent's variables, thus starting with an internal set of
shell variables[1].
These shell variables in Bash can be exported in order to become environment variables:
VARIABLE=content
export VARIABLE
or with a shortcut
export VARIABLE=content
Environment variables are conventionally placed in ~/.profile or /etc/profile so that other Bourne-compatible shells can use them.
See Environment variables for more general information.
Command line
Bash command line is managed by the separate library called Readline. Readline provides emacs and vi styles of
shortcuts for interacting with the command line, i.e. moving back and forth on the word basis, deleting words etc.
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It is also Readline's responsibility to manage history of input commands. Last, but not least, it allows you to create
macros.
Tab completion
Tab completion is the option to auto-complete typed commands by pressing Tab (enabled by default).
Single-tab
It may require up to three tab-presses to show all possible completions for a command. To reduce the needed
number of tab-presses, see Readline#Faster completion.
Common programs and options
By default, Bash only tab-completes commands, filenames, and variables. The package bash-completion extends
this by adding more specialized tab completions for common commands and their options, which can be enabled
by sourcing /usr/share/bash-completion/bash_completion (which has been already sourced in Arch's
/etc/bash.bashrc ). With bash-completion, normal completions (such as ls file.* Tab Tab ) will behave
differently; however, they can be re-enabled with compopt -o bashdefault program (see [2] and [3] for more
detail).
Customize per-command
Note Using the complete builtin may cause conflicts with bash-completion.
By default, Bash only tab-completes file names following a command. You can change it to complete command
names using complete -c :
~/.bashrc
complete -c man which
or complete command names and file names with -cf :
complete -cf sudo
See bash(1) § Programmable Completion for more completion options.
History
History completion
You can bind the up and down arrow keys to search through Bash's history (see: Readline#History and Readline
Init File Syntax):
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~/.bashrc
bind '"\e[A": history-search-backward'
bind '"\e[B": history-search-forward'
or to affect all readline programs:
~/.inputrc
"\e[A": history-search-backward
"\e[B": history-search-forward
History customization
The HISTCONTROL variable can prevent certain commands from being logged to the history.
To stop logging of consecutive identical commands:
~/.bashrc
export HISTCONTROL=ignoredups
To remove all but the last identical command:
~/.bashrc
export HISTCONTROL=erasedups
To avoid saving commands that start with a space:
~/.bashrc
export HISTCONTROL=ignorespace
To avoid saving consecutive identical commands, and commands that start with a space:
~/.bashrc
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export HISTCONTROL=ignoreboth
To remove all but the last identical command, and commands that start with a space:
~/.bashrc
export HISTCONTROL="erasedups:ignorespace"
See bash(1) § HISTCONTROL for details.
Disable history
To disable the bash history only temporarily:
$ set +o history
The commands entered now are not logged to the $HISTFILE .
For example, now you can hash passwords with printf secret | sha256sum , or hide GPG usage like gpg -eaF
secret-pubkey.asc and your secret is not written to disk.
To enable history:
$ set -o history
To disable all bash history:
~/.bashrc or /etc/profile
export HISTSIZE=0
... and just to make sure, destroy your old histfile forever:
$ wipe -i -l2 -x4 -p4 "$HISTFILE"
$ ln -sv /dev/null "$HISTFILE"
Mimic Zsh run-help ability
Zsh can invoke the manual for the command preceding the cursor by pressing Alt+h . A similar behaviour is
obtained in Bash using this Readline bind:
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~/.bashrc
run-help() { help "$READLINE_LINE" 2>/dev/null || man "$READLINE_LINE"; }
bind -m vi-insert -x '"\eh": run-help'
bind -m emacs -x '"\eh": run-help'
This assumes are you using the (default) Emacs editing mode.
atuin replaces your existing shell history with an SQLite database, and records additional context for your
commands. Additionally, it provides optional and fully encrypted synchronization of your history between
machines, via an Atuin server.
Enable bash history timestamps ( export HISTTIMEFORMAT="%F %T " ) before syncing. Atuin works well with tools
like blesh-gitAUR and cmd-wrapped to provide an enhanced terminal experience across machines.
Aliases
alias is a command, which enables a replacement of a word with another string. It is often used for abbreviating a
system command, or for adding default arguments to a regularly used command.
Personal aliases can be stored in ~/.bashrc or any separate file sourced from ~/.bashrc . System-wide aliases
(which affect all users) belong in /etc/bash.bashrc . See [4] for example aliases.
For functions, see Bash/Functions.
Tips and tricks
Prompt customization
See Bash/Prompt customization.
Syntax highlighting and autosuggestions
ble.sh (Bash Line Editor), packed as blesh-gitAUR, is a command line editor written in pure Bash, which is an
alternative to GNU Readline. It has many enhanced features like syntax highlighting, autosuggestions, menu-completion, abbreviations, Vim editing mode, and hook functions. Other interesting features include status line,
history share, right prompt, transient prompt, and xterm title.
After installing it, source it in an interactive session.
~/.bashrc
source /usr/share/blesh/ble.sh
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Configurations are explained in depth in the ~/.blerc file and at the wiki. The stable bleshAUR
 package is also
available.
Command not found
pkgfile includes a "command not found" hook that will automatically search the official repositories, when
entering an unrecognized command.
You need to source the hook to enable it, for example:
~/.bashrc
source /usr/share/doc/pkgfile/command-not-found.bash
Then attempting to run an unavailable command will show the following info:
$ abiword
abiword may be found in the following packages:
 extra/abiword 3.0.1-2 /usr/bin/abiword
Note The pkgfile database may need to be updated before this will work. See pkgfile#Installation for details.
Disable Ctrl+z in terminal
You can disable the Ctrl+z feature (pauses/closes your application) by wrapping your command like this:
#!/bin/bash
trap "" 20
adom
Now, when you accidentally press Ctrl+z in adomAUR instead of Shift+z , nothing will happen because
Ctrl+z will be ignored.
Clear the screen after logging out
To clear the screen after logging out on a virtual terminal:
~/.bash_logout
clear
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reset
Auto "cd" when entering just a path
Bash can automatically prepend cd when entering just a path in the shell. For example:
$ /etc
bash: /etc: Is a directory
But after adding one line into .bashrc file:
~/.bashrc
...
shopt -s autocd
...
You get:
[user@host ~]$ /etc
cd /etc
[user@host etc]$
Autojump
autojump-gitAUR is a python script which allows navigating the file system by searching for strings in a database
with the user's most-visited paths.
zoxide is an alternative which has additional features and performance improvements compared to the original
autojump and can serve as a drop-in replacement for autojump.
Prevent overwrite of files
For the current session, to disallow existing regular files to be overwritten by redirection of shell output:
$ set -o noclobber
This is identical to set -C .
To make the changes persistent for your user:
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~/.bashrc
...
set -o noclobber
To manually overwrite a file while noclobber is set:
$ echo "output" >| file.txt
Use directory stack to navigate
pushd and popd can be used to push or pop directories to a stack while switching to them. This can be useful
for "replaying" your navigation history.
[user@host ~] pushd /tmp/dir1
[user@host /tmp/dir1] pushd /var/lib
[user@host /var/lib] popd
[user@host /tmp/dir1] popd
[user@host ~]
See bash(1) § DIRSTACK.
Shell environment detection
See Environment variables#Shell environment detection.
Troubleshooting
Line wrap on window resize
When resizing a terminal emulator, Bash may not receive the resize signal. This will cause typed text to not wrap
correctly and overlap the prompt. The checkwinsize shell option checks the window size after each command
and, if necessary, updates the values of LINES and COLUMNS .
~/.bashrc
shopt -s checkwinsize
Shell exits even if ignoreeof set
If you have set the ignoreeof option and you find that repeatedly hitting ctrl-d causes the shell to exit, it is
because this option only allows 10 consecutive invocations of this keybinding (or 10 consecutive EOF characters,
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to be precise), before exiting the shell.
To allow higher values, you have to use the IGNOREEOF variable.
For example:
export IGNOREEOF=100
Checking errors by analyzing scripts
The package shellcheck analyzes bash (and other shell) scripts, prints possible errors, and suggests better coding.
There is also the web site shellcheck.net of the same purpose, based on this program.
See also
Bash Reference Manual, or /usr/share/doc/bash/bashref.html
Readline Init File Syntax
The Bourne-Again Shell - The third chapter of The Architecture of Open Source Applications
PS1 generator - generate your .bashrc/PS1 bash prompt using an intuitive UI
Even more useful .bashrc commands
Tutorials
Greg's Wiki
GregsWiki:BashGuide
GregsWiki:BashFAQ
Quote Tutorial
An active and friendly IRC channel for Bash
Examples
How to change the title of an xterm
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