What is the difference between .bash_profile and .bashrc?

.bash_profile is executed for login shells, while .bashrc is executed for interactive non-login shells.

When you login (type username and password) via console, either sitting at the machine, or remotely via ssh: .bash_profile is executed to configure your shell before the initial command prompt.

But, if you’ve already logged into your machine and open a new terminal window (xterm) then .bashrc is executed before the window command prompt. .bashrc is also run when you start a new bash instance by typing /bin/bash in a terminal.

On OS X, Terminal by default runs a login shell every time, so this is a little different to most other systems, but you can configure that in the preferences.

X11 will look at your .bashrc while a "regular" Terminal will look at .bash_profile

However, if you add the following to your .bash_profile, you can then move everything into your .bashrc file so as to consolidate everything into one place instead of two:

if [ -f $HOME/.bashrc ]; then
        source $HOME/.bashrc
fi

For macOS, the code to put into .bash_profile to consolidate everything into .bashrc is the following:

if [ -f ~/.bashrc ]; then
    source ~/.bashrc
fi

This is more specific for Mac terminal user.

TLDR; use .bash_profile for your aliases.

The way the different initialisation files work together is a bit more complicated, and there are some important special cases in OSX. Here are the highlights:

• Bash, on any platform, executes one of several different files depending on how it is invoked. The details are here.
• OSX's Terminal App does something non-standard: it creates every new tab or window as if it were a login shell, which means that .bash_profile is called. Thus the TLDR advice above.
• .bashrc is also an option, but that will be called every time you create a subshell (i.e., invoke bash), which can create inefficiency if you update a variable within it (e.g., PATH=/bin/foo:$PATH)
• Other apps that have embedded terminals can choose to follow Terminal App's convention or not. Notably, Visual Studio Code, by default, does not.
• Apps invoked via the GUI are not spawned from a shell. Thus, there are several competing mechanisms for setting environment variables for them to see, which have changed over the years.
• Snippets that call .bashrc from .bash_profile are quite common.