Shell builtins · bash builtin

`alias`

Define a short name that the shell replaces with a longer command line, or list the aliases already defined.

alias [-p] [NAME[=VALUE] ...]

10 of 10 examples run in Debian 13.7 on 2026-10-31 · manual: bash(1), SHELL BUILTIN COMMANDS

An alias is a text substitution done by the shell's parser: when the first word of a simple command matches an alias name, the shell swaps in the alias value before doing anything else. alias ll='ls -l' makes ll data run ls -l data. Aliases are meant for interactive typing; they live in ~/.bashrc and save keystrokes.

Because the substitution happens while the line is being read, two rules follow. An alias is only recognized in the command position (the first word), and an alias defined on a line takes effect only for lines read after it. Non-interactive shells, which includes every script and every bash -c, ignore aliases completely unless you run shopt -s expand_aliases. The examples on this page do exactly that.

For anything with arguments in the middle, logic, or use in scripts, write a function instead (ll() { ls -l "$@"; }). Functions work everywhere, take arguments anywhere, and do not depend on parse timing. To remove an alias use unalias NAME; to bypass one for a single command, prefix it with a backslash (\ls) or use command.

Examples

Define and use an alias

$ shopt -s expand_aliases
> alias lt='ls -t'
> lt data | head -n 3

output

users.csv
poem.txt
windows.txt

lt data is rewritten to ls -t data before it runs. The shopt line is needed only because examples run non-interactively; in your terminal aliases are on by default.

Aliases do nothing in scripts by default

$ alias greet='echo hello'
> greet

outputexit 127

/bin/bash: line 2: greet: command not found

A non-interactive bash (a script, bash -c, cron) defines the alias but never expands it, so greet is looked up as a command and is not found. This is the reason an alias from your .bashrc "does not work" in a script.

An alias is not available on the line that defines it

$ shopt -s expand_aliases
> alias hi='echo hi there'; hi
> hi

output

/bin/bash: line 2: hi: command not found
hi there

The whole first line is parsed before alias runs, so hi on that line is looked up as a command and fails with status 127. On the next line, read after the definition, the alias expands. The same applies inside a function body or an if block: the whole block is parsed at once.

List the defined aliases

$ alias ll='ls -l' la='ls -A' gs='git status'
> alias

output

alias gs='git status'
alias la='ls -A'
alias ll='ls -l'

With no arguments, alias prints every alias in a form that could be pasted back into the shell, sorted by name. alias -p does the same. Several aliases can be defined in one command.

Show one alias

$ alias ll='ls -l'
> alias ll
> alias nope

outputexit 1

alias ll='ls -l'
/bin/bash: line 3: alias: nope: not found

Given only a name, alias prints that definition. An unknown name is an error, so the exit status is 1.

Arguments always go at the end

$ shopt -s expand_aliases
> alias count='wc -l'
> count todo.txt notes.txt

output

  5 todo.txt
  6 notes.txt
 11 total

Whatever follows the alias name is appended after the replacement text. There is no way to put an argument in the middle of an alias; that is the point where a function is the right tool.

Use a function when you need arguments

$ errors() { grep -c "ERROR" "$@"; }
> errors logs/app.log
> errors -h logs/app.log logs/error.log

output

2
2
0

A function receives its arguments in $@ and can place them anywhere. It works in scripts without any shopt, and options such as -h pass straight through.

Bypass an alias for one command

$ shopt -s expand_aliases
> alias ls='ls -F'
> ls scripts
> \ls scripts
> command ls scripts

output

backup.sh*
greet.sh*
backup.sh
greet.sh
backup.sh
greet.sh

With the alias, ls appends * to executables. A backslash on the command name, or quoting any part of it, prevents alias lookup, as does running it through command.

Make the next word alias-expanded too with a trailing space

$ shopt -s expand_aliases
> alias ll='ls -l'
> alias run='time -p '
> run ll -d data

output

drwxrwxr-x 2 dev dev 13 Oct 25 01:33 data
real 0.00
user 0.00
sys 0.00

Only the first word is normally checked for aliases. When an alias value ends in a space, the word after it is checked too, so ll expands after run. This is why people define alias sudo='sudo '.

Remove an alias

$ alias ll='ls -l' la='ls -A'
> unalias ll
> alias
> unalias -a
> alias | wc -l

output

alias la='ls -A'
0

unalias NAME removes one alias; unalias -a removes them all. Useful at the top of a sourced file that wants predictable commands.

Common pitfalls

Expecting aliases in scripts. A non-interactive bash ignores them; even with shopt -s expand_aliases they apply only to lines read after the definition. Write a function.
Defining an alias and using it on the same line, or inside the same function or compound command: it is not expanded until the next separately parsed command.
Double quotes expand variables when the alias is defined: alias here="cd $PWD" freezes the current directory. Single quotes defer expansion to each use.
An alias that shadows a command, such as alias rm='rm -i', trains you to rely on a safety net that is missing on other machines and in scripts.

GNU vs BSD and macOS

The examples above ran the GNU/Linux version. These are the differences that matter on macOS and the BSDs (written from their documentation, not run here).

Aliases exist in every POSIX shell with the same syntax. zsh expands aliases in scripts by default and also has global aliases (alias -g); dash honors them in scripts without any option.

Options worth knowing

A selection, described in our own words. For the full list, see bash(1), SHELL BUILTIN COMMANDS.

Option	What it does
`-p`	Print all aliases in reusable alias NAME=VALUE form.

Examples

Common pitfalls

GNU vs BSD and macOS

Options worth knowing

Related