add a directory to your PATH

at the end:

export PATH=$PATH:/my/dir

at the beginning:

export PATH=/my/dir/:$PATH

in fish:

set -e PATH $PATH /my/dir

(illustration of a little fish with a heart-shaped tail)

you shell’s config file

bash: .bashrc or .bash_profile (exactly which one is a bit of a rabbit hole sadly)

zsh: ~/.zshrc

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

(illustration of a little fish with a heart-shaped tail)

show what your shell is actually going to do when you run the program

type python3

instead of running what’s in PATH, sometimes it’ll run a builtin or alias or cached entry

show the first match on your PATH for a program

which python3

(but in zsh which acts like type)

show ALL matches on your PATH for a program, in order

which -a python3

look at your PATH

echo $PATH

show each entry on its own line

echo $PATH | tr ':' '\n'

clear the PATH cache (bash/zsh)

hash -r

why you might need to do this: bash and zsh cache PATH lookups, so sometimes updating your PATH doesn’t work properly