50.2 The apropos Command

The biggest problem with the UNIX manual set is finding what you want, given that you don't already know what you're looking for. For example: you want to search for a string in a file. If you don't remember that the command you want is called grep , how will you ever find it?

The apropos command, which is equivalent to man -k (and sometimes just an alias for man -k ) helps to solve this problem. It's not always successful, but it's better than nothing. It looks through headings of all the "man pages" and prints any that match a given keyword. For example, to figure out how to search for a string, try the command:

% 

apropos string

 ... gets, fgets (3S)        - get a string from a stream getsubopt (3)           - parse sub options from a string gettext, textdomain (3) - retrieve a message string, get & set text domain grep, egrep, fgrep (1V) - search a file for a string or regular expression puts, fputs (3S)        - put a string on a stream ...

We've cut some of the output for convenience, but you can see what you want: to search for a string, you clearly want to use grep or one of its relatives.

All BSD and SVR4 systems support apropos . However, there are plenty of SVR3 (and earlier) systems kicking around that don't. If you're facing this problem, see article 50.3 .

MILD FLAME: Over the years, the output from apropos has gotten quite cluttered. It's considerably less useful now than it was ten years ago.