25: The $PATH environment variable

  Wurm lab

One other use of the echo command is for displaying the contents of something known as environment variables. These contain user-specific or system-wide values that either reflect simple pieces of information (your username), or lists of useful locations on the file system. Some examples:

learner@:learning_unix$ echo $USER
learner
learner@:learning_unix$ echo $HOME
/home/learner
learner@:learning_unix$ echo $PATH
/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin

The last one shows the content of the $PATH environment variable, which displays a colon separated list of directories that are expected to contain programs that you can run. This includes all of the Unix commands that you have seen so far. These are files that live in directories which are run like programs (e.g. ls is just a special type of file in the /bin directory).

Knowing how to change your $PATH to include custom directories can be necessary sometimes (e.g. if you install some new software in a non-standard location).