For example: man(1)
, find(3)
, updatedb(2)
?
What do the numbers in parentheses (Brit. "brackets") mean?
It's the section that the man page for the command is assigned to.
These are split as
Original descriptions of each section can be seen in the Unix Programmer's Manual (page ii).
In order to access a man page given as "foo(5)", run:
man 5 foo
As @Ian G says, they are the man page sections. Let's take this one step further though:
man
command with man man
, and it shows the 9 sections as follows:DESCRIPTION
man is the system's manual pager. Each page argument given
to man is normally the name of a program, utility or func‐
tion. The manual page associated with each of these argu‐
ments is then found and displayed. A section, if provided,
will direct man to look only in that section of the manual.
The default action is to search in all of the available sec‐
tions following a pre-defined order ("1 n l 8 3 2 3posix 3pm
3perl 5 4 9 6 7" by default, unless overridden by the SEC‐
TION directive in /etc/manpath.config), and to show only the
first page found, even if page exists in several sections.
The table below shows the section numbers of the manual fol‐
lowed by the types of pages they contain.
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 conven‐
tions), e.g. man(7), groff(7)
8 System administration commands (usually only for root)
9 Kernel routines [Non standard]
A manual page consists of several sections.
man <section_num> <cmd>
Let's imagine you are Googling around for Linux commands. You find the OPEN(2)
pg online: http://man7.org/linux/man-pages/man2/open.2.html.
To see this in the man pages on your pc, simply type in man 2 open
.
For FOPEN(3)
use man 3 fopen
, etc.
man <section_num> intro
To read the intro pages to a section, type in man <section_num> intro
, such as man 1 intro
, man 2 intro
, man 7 intro
, etc.
To view all man page intros in succession, one-after-the-other, do man -a intro
. The intro page for Section 1 will open. Press q to quit, then press Enter to view the intro for Section 8. Press q to quit, then press Enter to view the intro for Section 3. Continue this process until done. Each time after hitting q, it'll take you back to the main terminal screen but you'll still be in an interactive prompt, and you'll see this line:
--Man-- next: intro(8) [ view (return) | skip (Ctrl-D) | quit (Ctrl-C) ]
Note that the Section order that man -a intro
will take you through is:
This search order is intentional, as the man man
page explains:
The default action is to search in all of the available sections follow‐
ing a pre-defined order ("1 n l 8 3 2 3posix 3pm 3perl 5 4 9 6 7" by default, unless overrid‐
den by the SECTION directive in /etc/manpath.config)
Why did they choose this order? I don't know (please answer in the comments if you know), but just realize this order is correct and intentional.
It indicates the section of the man pages the command is found in. The -s switch on the man command can be used to limit a search to certain sections.
When you view a man page, the top left gives the name of the section, e.g.:
User Commands printf(1)
Standard C Library Functions printf(3C)
So if you are trying to look up C functions and don't want to accidentally see a page for a user command that shares the same name, you would do 'man -s 3C ...'
Wikipedia details about Manual Sections: