the shell starts programs

when you run a program in the terminal, you’re actually asking your shell to start it for you

it turns out that starting programs is a surprisingly complicated job!

the 3 most popular shells

there are LOTS of shells but 95% of people use

• bash (default on Linux)
• zsh (default on Mac (in 2025))
• fish (aims to be more user friendly)

fish: the friendly interactive shell

ASCII illustration of a fish

I love how fish has friendly defaults that I can use without configuring it

this is (mostly) not a fish propaganda zine though

Little illustration of a smiling stick figure holding up a sign that says “fish 4eva”, labelled “me”

bash and zsh are both “POSIX shells”

this means they follow a standard for how Unix shells should behave, but there are differences

I’ll mention when something varies between shells!

where to find your shell’s config file

bash: ~/.bashrc or ~/.bash_profile (which one is a rabbit hole, huge flow chart at wzrd.page/bashrc)

zsh: ~/.zshrc

fish: ~/.config/fish/config.fish

.bashrc vs .bash_profile

here’s an trick to figure out whether bash is using .bashrc or .bash_ profile (or both!)

Add:

echo "this is .bashrc"
echo "this is . bash _ profile"

to each file, open a new terminal tab, and see what it prints out!