In Unix, what is my path, and how do I set or modify it?

The PATH environment variable is a colon-delimited list of directories that your shell searches through when you enter a command.

Program files (executables) are kept in many different places on the Unix system. Your path tells the Unix shell where to look on the system when you request a particular program. Having more directories in your path will reduce the number of times you get "Command not found" errors, but might put you at greater risk of activating a Trojan horse.

To find out what your path is, at the Unix shell prompt, enter:

  echo $PATH

Your path will look something like the following.

  /usr2/username/bin:/usr/local/bin:/usr/bin:.

You will see your username in place of username. Using the above example path, if you enter the ls command, your shell will look for the appropriate executable file in the following order: first, it would look through the directory /usr2/username/bin, then /usr/local/bin, then /usr/bin, and finally the local directory, indicated by the . (a period).

To modify your path

If you are using csh or tcsh, at the shell prompt, enter:

  setenv PATH $PATH\:/dir/path

If you are using sh, ksh, or bash, at the shell prompt, enter:

  PATH=$PATH\:/dir/path ; export PATH

In all cases, replace /dir/path with the directory you want the shell to search.

To make these changes permanent, add the commands described above to the end of your .cshrc file (for csh and tcsh), .profile file (for sh and ksh), or .bash_profile file (for bash).