Guide to Unix/Commands/Getting Help

man
Displays the manual page for the specified command

A useful option is: $ man -k TEXT

This searches manual page titles and synopsis lines for TEXT

Examples:

To display the manual page for the chown command:

$ man chown

man has different sections.
 * section 1 is user commands
 * section 2 is system calls (used by programs to communicate with the kernel)
 * section 3 is library reference (for programming in C)
 * section 4 is device drivers
 * section 5 is configuration files and other file formats
 * section 6 is games
 * section 7 is miscellaneous (for example, "ascii" map and C "operator" precedence)
 * section 8 is system commands (like user commands, but mostly for root)

A section number can be specified before the page name. For example, man chmod normally shows the user command "chmod". To see the system call "chmod": $ man 2 chmod

To search the man pages for "newsgroups",

$ man -k newsgroups actsync             (8)  - synchronize newsgroupsoups newsgroups          (1)  - a program to list unsubscribed newsgroups


 * If this does not work you may have to run the makewhatis command.

Links:
 * man, opengroup.org
 * man man page, man.cat-v.org

info
An advanced man command that is sometimes available. It displays the improved manual pages in Info format for specified command. Seems absent from POSIX.

Examples:

To display the manual page for the grep command:

$ info grep

To find occurrence of 'grep' in all info manual pages:

$ info --apropos grep "(autoconf-2.13)Examining Declarations" -- EGREP_CPP "(autoconf-2.13)Examining Declarations" -- EGREP_HEADER "(autoconf-2.13)Old Macro Names" -- HEADER_EGREP ...

To see the physical location of 'grep' info manual page:

$ info -w grep /usr/share/info/grep.info.gz To view a file a info page:

$ info -f ./some_cmd.info.gz

Links:
 * info man pag, freebsd.org
 * info man page, manpages.ubuntu.com
 * Stand-alone GNU Info 6.2 - GNU manual, gnu.org

apropos
Searches the manual page short descriptions for a specified keyword. Seems absent from POSIX.

On many systems this is exactly the same as the -k option of the man command.

Examples:

$ apropos newsgroups active              (5)  - list of active Usenet newsgroups newsgroups          (1)  - a program to list unsubscribed newsgroups

Links:
 * apropos man page, freebsd.org

whatis
Displays short man page descriptions. Seems absent from POSIX.

Examples:

$ whatis info info (1)            - read Info documents info (5)            - readable online documentation

$ whatis chmod chmod (1) - change file modes chmod, fchmod (2) - change mode of file

Links:
 * whatis man page, freebsd.org

makewhatis
Creates the database for the whatis, apropos, and man -k commands. This is commonly run automatically by your system however sometimes you need to run this manually. Seems absent from POSIX.

Examples:


 * 1) makewhatis

$ sudo makewhatis

Links:
 * makewhatis man page, freebsd.org