man - Linux

Overview

The man command in Linux stands for manual, and it is utilized to display the user manual of any command that Linux supports. It fetches documentation in real time and displays it, allowing users to understand the functionality and options of commands. It is particularly useful for new users learning Linux commands, as well as experienced users who need to check the details or usage options of less familiar commands.

Syntax

The basic syntax of the man command is:

man [options] [command_name]

Where:

  • [options] are the flags and modifiers that control the output,
  • [command_name] is the name of the command you want to get information on.

Options/Flags

  • -k: Search the short descriptions and manual page names for the keyword, as the apropos command does.
  • -f: Equivalent to whatis. Display concise description of the command.
  • -t: Use /usr/bin/groff -Tps -mandoc to format the manual page, enabling direct printing from the command line.
  • -K: Search for text in all manual pages. This is useful for finding specific functionality.
  • -w or --path: Show the location of the man page files, rather than showing the man pages themselves.
  • -P pager: Specify which pager to use. The default is less.
  • -c: Reformat the source manual page, useful for viewing source edits.

If no options are specified, man defaults to displaying the manual page for the specified command.

Examples

  1. Basic Usage:
    View the manual page of the ls command:

    man ls
  2. Searching with Keywords:
    Find manual pages including the keyword “copy”:

    man -k copy
  3. Viewing System Calls (category 2 in the manual pages): 
    man 2 intro

Common Issues

  • Manual pages not found: This may occur if the manual pages are not installed. On many distributions, you may need to install the man-pages package, for example on Ubuntu: 
    sudo apt install manpages
  • Misformatted output: Ensure your terminal is using a monospace font and check if you have correct pager software installed like less.

Integration

man can be integrated with other commands like grep to search for specific options within a command’s manual page:

man [command_name] | grep -A3 [search_term]

This is helpful to quickly find information without scrolling through entire manual pages.

  • apropos: Search the manual page names and descriptions.
  • whatis: Display one-line manual page descriptions.
  • info: Read Info documents, which provide a different format of documentation.

For further reading and information, consult the official Linux documentation and man-page project at your distribution’s website or the Linux man-pages project online.