Unix Environment Variables

Let’s talk about some popular unix environment variables:

The most important one is probably $PATH, which is where the OS looks for binaries. It goes from the beginning to the end, executing the first binary it finds.

Let’s say my $PATH is like this:


Which instructs the OS to look into /usr/local/bin to find a valid binary. Then /usr/bin.

The /bin directory contains binaries for sysadmins and users, but are required when there’s no filesystem in use.

The /usr/bin and was meant to contain executable programs that were part of the OS

and /usr/local/bin is for software that the user installs.

There directories where superuser binaries should be located which follow the same scheme:

As well, /usr/share/bin is for binaries used for web servers and clients.

If you find that a command doesn’t work, double-check to make sure that your $PATH is set up properly to find the correct binary.