Using Aliases in Bash

What are aliases in bash?

If you are tired of typing out the same long command over and over again, it’s time to set up a few bash aliases. Aliases allow you to create shortcut commands for longer ones. For example, instead of typing out ls -l, you could type ll + Enter to save time.

How do you set up an alias?

In order to set up an alias, you will need to be familiar with a text editor (like vim!) and the .bashrc or .bash_profile files. On Unix operating systems, these files will typically be located in the user’s home directory. There is a subtle difference between these two files, which is related to the difference between login and non-login shells (which is not important for now):

• The .bashrc file is reloaded every time you start a new copy of Bash.
• The .bash_profile file is loaded only when you log in (or use a flag to tell Bash to act as a login shell).

It is typical to put aliases into the .bashrc file, and to reference your .bashrc file in the .bash_profile. If you ever make changes to your .bashrc, you just need to type bash into the command line to reload the file.

A bash alias has the following structure:

alias [alias_name]="[long_command_to_alias]"

Each alias is on a new line and begins with the command alias, followed by your desired shortcut, an =, and then the full command that you do not want to type anymore.

Example:

Using combinations of options with ls on the command line is very useful, but can get clunky. A common command is: ls -lhaG. (This tells the shell to list the contects of a directory in long format, showing hidden files, with human-readable sizes, and hide the group names.) Instead of typing ls -lhaG everytime, it would be much easier to type ll.

$ vi ~/.bashrc

This will open your .bashrc file in vim. Now that you are in vim, or whatever text editor you prefer, add the following:

alias ll="ls -lhaG"

Save and close the .bashrc file now. Since we’ve added this to the .bashrc file, we now need to type bash and Enter on the command line, and now the alias will be live. Try typing ll to see what happens.

What are my favorite aliases?

I use aliases for ssh commands, common bash command combinations, and for moving around common directories.

SSH to a remote server: alias server="ssh fnn@made.up.server.edu"

Changing directories to my home base from any location: alias wrk="cd /my/working/directory"

Starting Rstudio Server alias rstud="/programs/rstudio_server/rstudio_start"

More information and examples

There are many guides available online for setting up and understanding aliases.

You can see nixCraft’s list of 30 useful aliases for bash here.

DigitalOcean has also published examples of useful aliases.

And finally, you can find similar information and a video on aliases here.