Engineering Craft › Developer Tooling

PATH

The list of directories the shell searches for commands.

Also known as: PATH environment variable, $PATH, command not found

PATH is an environment variable that holds a list of directories. When you type a command like python or git, the shell looks through those directories, in order, for a program with that name, and runs the first one it finds.

echo $PATH
# /usr/local/bin:/usr/bin:/bin:/home/ana/.local/bin

which python          # which file will run?
type -a python        # every match on the PATH, in order

Directories are separated by : (on Windows, ;).

“command not found”

The classic error means the program isn’t in any listed directory. Either it isn’t installed, or its folder isn’t on the PATH.

export PATH="$HOME/.local/bin:$PATH"      # add a folder to the front, for this shell

To make it permanent, put that line in your shell’s startup file (~/.bashrc, ~/.zshrc), then open a new terminal.

Order matters

The first match wins, so putting a folder at the front lets its programs override system ones. That’s how version managers and virtual environments work: they put their own bin directory first.

which python      # /usr/bin/python        (system)
source .venv/bin/activate
which python      # /project/.venv/bin/python

Tips

• “It works in one terminal, not another”: the PATH differs. Check echo $PATH in each, and where it’s set.
• Use full paths in scripts and cron jobs, which often run with a minimal PATH.
• Don’t add . (the current directory) to the PATH. It lets a malicious file in a folder run by accident.
• Install tools in one predictable place, instead of piling directories into PATH.
• Editors and GUI apps may not see the PATH from your shell config, which causes “works in the terminal, fails in the IDE”.