whatis

Display a description from a man page

$ whatis [command]

$ whatis -l [command]

$ whatis -w net*

$ whatis -r 'wish[0-9]\.[0-9]'

$ whatis -L en [command]

whatis [-dlv] [-r | -w] [-s list] [-m system] [-M path] [-L locale] name...

whatis searches the manual page names and displays brief descriptions from the NAME section of matching man pages. It queries the whatis database, a cache of manual page descriptions built by mandb.
The command is useful for quickly determining what a command does without reading the full manual page. Multiple commands can be queried at once, and pattern matching allows searching for groups of related commands.

-d, --debug

Enable debug mode

Do not trim output to terminal width

Interpret name as a regular expression

Interpret name as a shell glob pattern

Search only specified manual sections

Search man pages from other systems

Set manual page search path

Set locale for searching

Print verbose warning messages

Requires the whatis database to be built (usually done automatically by mandb). Results may be incomplete if the database is out of date. Use mandb to rebuild the database if necessary.

Derived from BSD Unix as part of the man page system. The whatis database was introduced to speed up lookups compared to scanning all man pages. On modern systems, mandb maintains the database, replacing older makewhatis implementations.

man(1), apropos(1), whereis(1), mandb(8)