bash Cookbook

Finding and Running Commands

Problem

You need to find and run a particular command under bash.

Solution

Try the type, which, apropos, locate, slocate, find, and ls commands.

Discussion

bash keeps a list of directories in which it should look for commands in an environment variable called $PATH. The bash built-in type command searches your environment (including aliases, keywords, functions, built-ins, and files in the $PATH) for executable commands matching its arguments and displays the type and location of any matches. It has several arguments, notably the -a flag, which causes it to print all matches instead of stopping at the first one. The which command is similar but only searches your $PATH (and csh aliases). It may vary from system to system (it’s usually a csh shell script on BSD, but a binary on Linux), and usually has a -a flag like type. Use these commands when you know the name of a command and need to know exactly where it’s located, or to see if it’s on this computer. For example:

$ type which
which is hashed (/usr/bin/which)

$ type ls
ls is aliased to `ls -F -h'

$ type -a ls
ls is aliased to `ls -F -h'
ls is /bin/ls

$ which which
/usr/bin/which

Almost all commands come with some form of help on how to use them. Usually there is online documentation called manpages, where “man” is short for manual. These are accessed using the man command, so man ls will give you documentation about the ls command. Many programs also have a built-in help facility, accessed by providing a ...