whatis: One-Line Command Summaries (Unix Power Tools, 3rd Edition)

2.2. whatis: One-Line Command Summaries

whatis is almost identical to apropos or the use of man -k (Section 2.1), but it requires a command name as an argument -- rather than an arbitrary string. Why is this useful? Well, let's say you forget what cat (Section 12.2) does. On my system, apropos cat gives you several screenfuls of output. You may not want to read the entire manual page. But whatis cat gives you a nice one-line summary:

% whatis cat
cat (1V)      - concatenate and display

The whatis command is equivalent to man -f on most systems.

Before running whatis the first time on your system -- particularly if you're running a standalone machine using FreeBSD, Linux, or Darwin -- you'll want to run the makewhatis at /usr/libexec/makewhatis, which creates the whatis database by scanning the command names from the existing manpages.

-- ML