man pages

(Written by Paul Cobbaut, https://github.com/paulcobbaut/)

This chapter will explain the use of man pages (also called manual pages) on your Unix or Linux computer.

You will learn the man command together with related commands like whereis, whatis and mandb.

Most Unix files and commands have pretty good man pages to explain their use. Man pages also come in handy when you are using multiple flavours of Unix or several Linux distributions since options and parameters sometimes vary.

man $command

Type man followed by a command (for which you want help) and start reading. Press q to quit the manpage. Some man pages contain examples (near the end).

student@linux:~$ man whois
Reformatting whois(1), please wait...

man $configfile

Most configuration files have their own manual.

student@linux:~$ man syslog.conf
Reformatting syslog.conf(5), please wait...

man $daemon

This is also true for most daemons (background programs) on your system..

student@linux:~$ man syslogd
Reformatting syslogd(8), please wait...

man -k (apropos)

man -k (or apropos) shows a list of man pages containing a string.

student@linux:~$ man -k syslog
lm-syslog-setup (8)  - configure laptop mode to switch syslog.conf ...
logger (1)           - a shell command interface to the syslog(3) ...
syslog-facility (8)  - Setup and remove LOCALx facility for sysklogd
syslog.conf (5)      - syslogd(8) configuration file
syslogd (8)          - Linux system logging utilities.
syslogd-listfiles (8) - list system logfiles

whatis

To see just the description of a manual page, use whatis followed by a string.

student@linux:~$ whatis route
route (8)            - show / manipulate the IP routing table

whereis

The location of a manpage can be revealed with whereis.

student@linux:~$ whereis -m whois
whois: /usr/share/man/man1/whois.1.gz

This file is directly readable by man.

student@linux:~$ man /usr/share/man/man1/whois.1.gz

man sections

By now you will have noticed the numbers between the round brackets. man man will explain to you that these are section numbers. Executable programs and shell commands reside in section one.

1 Executable programs or shell commands
2 System calls (functions provided by the kernel)
3 Library calls (functions within program libraries)
4 Special files (usually found in /dev)
5 File formats and conventions eg /etc/passwd
6 Games
7 Miscellaneous (including macro packages and conventions), e.g. man(7)
8 System administration commands (usually only for root)
9 Kernel routines [Non standard]

man $section $file

Therefor, when referring to the man page of the passwd command, you will see it written as passwd(1); when referring to the passwd file, you will see it written as passwd(5). The screenshot explains how to open the man page in the correct section.

[student@linux ~]$ man passwd      # opens the first manual found
[student@linux ~]$ man 5 passwd    # opens a page from section 5

man man

If you want to know more about man, then Read The Fantastic Manual (RTFM).

Unfortunately, manual pages do not have the answer to everything...

student@linux:~$ man woman
No manual entry for woman

mandb

Should you be convinced that a man page exists, but you can\'t access it, then try running mandb on Debian/Mint.

root@linux:~# mandb
0 man subdirectories contained newer manual pages.
0 manual pages were added.
0 stray cats were added.
0 old database entries were purged.

Or run makewhatis on CentOS/Redhat.

[root@linux ~]# apropos scsi
scsi: nothing appropriate
[root@linux ~]# makewhatis 
[root@linux ~]# apropos scsi
hpsa                 (4)  - HP Smart Array SCSI driver
lsscsi               (8)  - list SCSI devices (or hosts) and their attributes
sd                   (4)  - Driver for SCSI Disk Drives
st                   (4)  - SCSI tape device