Unix provides hundreds of useful commands for all sorts of purposes, but it is sometimes difficult to find the specific command you are looking for.

To assist you with this task, most versions of Unix provide the `man -k` command.

The `man -k` command searches the online manual pages to help you find the Unix command for which you are looking.

For example, suppose you forgot the command to backup your Unix system. You might search for the word backup:

$ man -k backup dump(8), rdump(8) - file system backup restore(8), rrestore(8) - restore files or file systems from backups made with dump twfiles(5) - overview of files used by Tripwire and file backup process

Many Unix variants also provide the command `apropos`, which does the same thing as `man -k`.