Customizing the search path for commands: The PATH variable

Command interpreters usually have to search for a file that contains the command you want to run. When you are using the shell, you tell the shell where to search for a command. Essentially, the shell uses a list of directories in which commands may be found. This list is specified in your PATH variable in your etc/csh.cshrc file. The list could be called your search path, because it tells the shell where you want to search.

You can set up a search path with a command of the form: 
setenv path 'dir:dir:...'
or, 
set path=(dir1 dir2)
For example, you might enter: 
setenv path '/bin:/usr/bin:/usr/macneil/bin:/usr/games:/usr'
The shell then searches the directories in the following order, when looking for commands or shell scripts:
  1. /bin
  2. /usr/bin
  3. /usr/macneil/bin
  4. /usr/games
  5. /usr

As soon as the shell finds a file with an appropriate name, it runs that file.

Because the shell runs a command as soon as it finds a file with an appropriate name, pay close attention to the order in which you list directory names in your search path. For example, the previous search path specifies the /bin directory (where shell commands are stored) before the /usr/bin directory.

If you set up your PATH incorrectly, you could get the wrong command. You should generally search the shell commands directory first: /bin.