alias (command)

Non-persistent aliases can be created by supplying name/value pairs as arguments for the alias command. In Unix shells the syntax is:

alias gc='git commit'

The corresponding syntax in the C shell or tcsh shell is:

alias gc "git commit"

This alias means that when the command gc is read in the shell, it will be replaced with git commit and that command will be executed instead.

In the 4DOS/4NT shell the following syntax is used to define cp as an alias for the 4DOS copy command:

alias cp copy

To create a new alias in Windows PowerShell, the new-alias cmdlet can be used:

new-alias ci copy-item

This creates a new alias called ci that will be replaced with the copy-item cmdlet when executed.

In PowerShell, an alias cannot be used to specify default arguments for a command. Instead, this must be done by adding items to the collection $PSDefaultParameterValues, one of the PowerShell preference variables.

To view defined aliases the following commands can be used:

alias          # Used without arguments; displays a list of all current aliases
alias -p       # List aliases in a way that allows re-creation by sourcing the output; not available in 4DOS/4NT and PowerShell
alias myAlias  # Displays the command for a defined alias

In Unix shells, it is possible to override an alias by quoting any character in the alias name when using the alias. For example, consider the following alias definition:

alias ls='ls -la'

To override this alias and execute the ls command as it was originally defined, the following syntax can be used:

'ls'

or

\ls

In the 4DOS/4NT shell it is possible to override an alias by prefixing it with an asterisk. For example, consider the following alias definition:

alias dir = *dir /2/p

The asterisk in the 2nd instance of dir causes the unaliased dir to be invoked, preventing recursive alias expansion. Also the user can get the unaliased behaviour of dir at the command line by using the same syntax:

*dir

In Windows PowerShell, the set verb can be used with the alias cmdlet to change an existing alias:

set-alias ci cls

The alias ci will now point to the cls command.

In the 4DOS/4NT shell, the eset command provides an interactive command line to edit an existing alias:

eset /a cp

The /a causes the alias cp to be edited, as opposed to an environment variable of the same name.

In Unix shells and 4DOS/4NT, aliases can be removed by executing the unalias command:

unalias copy          # Removes the copy alias
unalias -a            # The -a switch will remove all aliases; not available in 4DOS/4NT
unalias *             # 4DOS/4NT equivalent of `unalias -a` - wildcards are supported

In Windows PowerShell, the alias can be removed from the alias:\ drive using remove-item:

remove-item alias:ci  # Removes the ci alias

An alias usually replaces just the first word. But some shells, such as bash and ksh, allow a sequence or words to be replaced. This particular feature is unavailable through the function mechanism.

The usual syntax is to define the first alias with a trailing space character. For instance, using the two aliases:

alias list='ls '      # note the trailing space to trigger chaining
alias long='-Flas'    # options to ls for a long listing

allows:

list long myfile      # becomes "ls -Flas myfile" when run

for a long listing, where "long" is also evaluated as an alias.

In the C Shell, arguments can be embedded inside the command using the string \!*. For example, with this alias:

 alias ls-more 'ls \!* | more'

ls-more /etc /usr expands to ls /etc /usr | more to list the contents of the directories /etc and /usr, pausing after every screenful. Without \!*,

 alias ls-more 'ls | more'

would instead expand to ls | more /etc /usr which incorrectly attempts to open the directories in more.[4]

The Bash and Korn shells instead use shell functions — see § Alternatives below.