Overview
`whatis` searches the manual page database for installed commands, functions, and file formats, and outputs a brief description of the matching entries. This is suitable for quickly checking what a command does before opening its full manual page with the `man` command.
Key Features
- Provides a one-line summary for commands/functions/file formats
- Searches the manual page database
- Supports quick information retrieval
Key Options
The `whatis` command offers several useful options to control the search behavior or specify particular manual sections.
Search and Output
Generated command:
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Description:
`whatis` Executes the command.
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Usage Examples
Various examples of how to use the `whatis` command.
Basic Usage
whatis lsCheck the summary information for the `ls` command.
Wildcard Search
whatis -w 'grep*'Find summary information for all commands starting with `grep`.
Search Specific Sections
whatis -s 1,5 passwdCheck information for the `passwd` command in user commands (section 1) and file formats (section 5).
Regular Expression Search
whatis -r 'user|group'Search for commands containing 'user' or 'group' using a regular expression.
Tips & Notes
Useful tips and points to note when using `whatis`.
Database Updates
whatis uses a manual page database. If new manual pages are installed or existing ones are updated, whatis might not find the information. In such cases, you need to update the database by running the sudo mandb command.
Update Manual Database
sudo mandbManually update the `whatis` database.
Difference from apropos
whatis searches for the first line of the manual page for the exact keyword specified, whereas apropos (equivalent to man -k) searches for keywords within the names and descriptions of manual pages. Therefore, apropos provides broader search results.