Linux and Unix alias command tutorial with examples

How to create shell aliases using bash or zsh to provide shortcuts to common commands

The UNIX and Linux alias command
The UNIX and Linux alias command

What is a shell alias?

A shell alias is a shortcut to reference a command. It can be used to avoid typing long commands or as a means to correct incorrect input. For common patterns it can reduce keystrokes and improve efficiency. A simple example is setting default options on commands to avoid having to type them each time a command is run.

Why create a shell alias?

For the following example suppose that a user prefers to confirm deleting a file before using the rm command. The rm command supports this with the -i option.

rm -i file.txt
remove file.txt? y

To avoid forgetting to use the -i option each time an alias can be created so that each time rm is run it will use the -i option and prompt the user to confirm.

How to set an shell alias

Building on the previous example an alias can be directly set in the shell as follows.

alias rm='rm -i'

Now when the rm command is run it will use the alias and the -i option.

rm file.txt
remove file.txt?

Note that setting an alias in this way only works for the life of a shell session. When the shell is closed the alias will be lost. To make an alias persist across shell sessions and reboots a configuration file for the shell should be used. For bash this is the .bashrc file. If you are using zsh it is the .zshrc file.

The .bashrc file

A .bashrc file can be used to set configuration for a shell. In this example a local user’s .bashrc file will be used. If you are running the zsh shell use a file called .zshrc.

Open the ~/.bashrc file in your preferred text editor. If it does not exist create it.

touch ~/.bashrc

How to add a shell alias to .bashrc

Within the .bashrc files aliases can now be added. The format is simple. First declare the command you wish to alias, then specify the command to run instead.

alias rm='rm -i'

For this example we replace rm with rm -i so that the user is prompted before deleting the file.

Once the .bashrc file is saved the shell needs to be reloaded for the alias to take effect.

source ~/.bashrc

The alias should now be available and typing rm will be interpreted as rm -i.

Some examples of aliases

The following are some practical examples of using aliases.

# ensure git commits are signed
alias git commit='git commit -S'

# shorthand for vim
alias v="vim"

# setting preferred options on ls
alias ls='ls -lhF'

# prompt user if overwriting during copy
alias cp='cp -i'

# prompt user when deleting a file
alias rm='rm -i'

# always print in human readable form
alias df="df -h"

Further reading


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