The system path

The list of directories your command interpreter works along, looking for the program whose name you’ve typed, is called the system path, and often just “the path”.

When you install a new program, the installation process will either put it in a directory that is already on the system path, or — if it makes a new directory — add the new directory to the path.

You can inspect and modify the system path on your own machine.

For example, to see the system path on Unix, do:

echo $PATH

In general, the system takes care of the path for you, so normally you don’t need to look at it. But it matters when you are having problems running a command (or perhaps being sure which version of a command you are running).