apropos (Unix)

apropos is a Unix command-line utility that searches the manual page descriptions for specified keywords. It provides a quick way to find commands related to a particular topic or function. Essentially, apropos performs a case-insensitive keyword search of the short descriptions found in the manual page index database.

When a user runs apropos with a keyword, it searches the whatis database (or an equivalent database) which contains brief descriptions of commands and functions. The database is typically generated by the makewhatis command or a similar utility.

The output of apropos consists of a list of commands or functions whose descriptions contain the specified keyword, along with their short descriptions and the section of the manual in which they are documented. This allows users to quickly identify relevant commands even if they do not know the exact name.

Apropos is useful for discovering commands related to a task, exploring the available tools for a specific purpose, and refreshing one's memory of commands they may have forgotten. It is often used when a user has a general idea of what they want to do but is unsure of the precise command to use. It’s a valuable tool for both beginners and experienced Unix users.

Compared to man -k (which essentially does the same thing), apropos is generally considered a more user-friendly alternative for performing keyword searches of manual pages.