How do I create a Bash alias?

I'm on OSX and I need to put something like this, alias blah="/usr/bin/blah" in a config file but I don't know where the config file is.

You can add an alias or a function in your startup script file. Usually this is .bashrc, .bash_login or .profile file in your home directory.

Since these files are hidden you will have to do an ls -a to list them. If you don't have one you can create one.

If I remember correctly, when I had bought my Mac, the .bash_login file wasn't there. I had to create it for myself so that I could put prompt info, alias, functions, etc. in it.

Here are the steps if you would like to create one:

1. Start up Terminal
2. Type cd ~/ to go to your home folder
3. Type touch .bash_profile to create your new file.
4. Edit .bash_profile with your favorite editor (or you can just type open -e .bash_profile to open it in TextEdit.
5. Type . .bash_profile to reload .bash_profile and update any alias you add.

I just open zshrc with sublime, and edit it.

subl .zshrc

And add this on sublime:

alias blah="/usr/bin/blah"

Run this command in terminal:

source ~/.zshrc

Done.

On OS X you want to use ~/.bash_profile. This is because by default Terminal.app opens a login shell for each new window.

See more about the different configuration files and when they are used here: What's the difference between .bashrc, .bash_profile, and .environment?

and in relation to OSX here: About .bash_profile, .bashrc, and where should alias be written in?

MacOS Catalina and Above

Apple switched their default shell to zsh, so the config files include ~/.zshenv and ~/.zshrc. This is just like ~/.bashrc, but for zsh. Just edit the file and add what you need; it should be sourced every time you open a new terminal window:

nano ~/.zshenv alias py=python

Then do ctrl+x, y, then enter to save.

This file seems to be executed no matter what (login, non-login, or script), so seems better than the ~/.zshrc file.

High Sierra and earlier

The default shell is bash, and you can edit the file ~/.bash_profile and add aliases:

nano ~/.bash_profile alias py=python

Then ctrl+x, y, and enter to save. See this post for more on these configs. It's a little better to set it up with your alias in ~/.bashrc, then source ~/.bashrc from ~/.bash_profile. In ~/.bash_profile it would then look like:

source ~/.bashrc