apropos

Search for a keyword using a regex

$ apropos [regex]

$ apropos [[-l|--long]] [regex]

$ apropos [regex_1] [[-a|--and]] [regex_2] [[-a|--and]] [regex_3]

apropos [OPTION...] KEYWORD...

-V, --version
    Display version info and exit

-r, --regex
    Interpret KEYWORD as regex

-e, --exact
    Like grep -w: exact word match

-w, --wildcard
    Wildcard pattern (* and ? supported)

-d, --search-dirs=DIRS
    Search specific man directories

-m, --systems=SYSTEMS
    Search other systems' man pages

-M, --manpath=PATHS
    Set search path for man pages

-C, --config-file=FILE
    Use specific config file

-O, --locale
    Use current locale for search

-R, --prompt
    Custom prompt string

-f, --exact-name
    Like whatis: match only page names

-K, --global-apropos
    Search all man page text (slow)

-L, --locale-lang
    Output in specific language

The apropos command searches the short descriptions in the NAME sections of manual pages (man pages) for keywords, listing matching pages with their names, sections, and descriptions. Ideal for discovering commands when you know the function but not the exact name.

It queries a pre-indexed database built from man pages, making searches fast. Output format is: section command - description.

Unlike man, which displays full pages, apropos provides an overview. Use multiple keywords for intersection (AND logic). It supports regex, exact, and wildcard matching via options. Essential for system administration, programming, and learning Linux/Unix tools.

Relies on mandb (formerly makewhatis) for database maintenance; outdated databases yield incomplete results. Commonly aliased as man -k.

Depends on updated mandb database; run sudo mandb or sudo makewhatis if results are incomplete. Searches only NAME sections by default (use -K for full text). Case-insensitive by default.

apropos keyword or man -k keyword for quick searches. Pipe to grep: apropos net | grep server.

Update with sudo mandb -t (creates temporary index) or cron jobs for automatic maintenance.

Originated in early Unix (1979 AT&T Version 7) as part of man utilities. Enhanced in man-db (1990s) for Linux with regex/wildcard support. Now standard in GNU man-db package.

man(1), whatis(1), mandb(8), manpath(1)