This page describes the conventions that should be employed when
writing man pages for the Linux man-pages project, which
documents the user-space API provided by the Linux kernel and the
GNU C library. The project thus provides most of the pages in
Section 2, many of the pages that appear in Sections 3, 4, and 7,
and a few of the pages that appear in Sections 1, 5, and 8 of the
man pages on a Linux system. The conventions described on this
page may also be useful for authors writing man pages for other
projects.
Sections of the manual pages
The manual Sections are traditionally defined as follows:
1 User commands (Programs)
Commands that can be executed by the user from within a
shell.
2 System calls
Functions which wrap operations performed by the kernel.
3 Library calls
All library functions excluding the system call wrappers
(Most of the libc functions).
4 Special files (devices)
Files found in /dev which allow to access to devices
through the kernel.
5 File formats and configuration files
Describes various human-readable file formats and
configuration files.
6 Games
Games and funny little programs available on the system.
7 Overview, conventions, and miscellaneous
Overviews or descriptions of various topics, conventions,
and protocols, character set standards, the standard
filesystem layout, and miscellaneous other things.
8 System management commands
Commands like mount(8), many of which only root can
execute.
Macro package
New manual pages should be marked up using the groff an.tmac
package described in man(7). This choice is mainly for
consistency: the vast majority of existing Linux manual pages are
marked up using these macros.
Conventions for source file layout
Please limit source code line length to no more than about 75
characters wherever possible. This helps avoid line-wrapping in
some mail clients when patches are submitted inline.
Title line
The first command in a man page should be a TH command:
.TH title section date source manual
The arguments of the command are as follows:
title The title of the man page, written in all caps (e.g., MAN-
PAGES).
section
The section number in which the man page should be placed
(e.g., 7).
date The date of the last nontrivial change that was made to
the man page. (Within the man-pages project, the
necessary updates to these timestamps are handled
automatically by scripts, so there is no need to manually
update them as part of a patch.) Dates should be written
in the form YYYY-MM-DD.
source The source of the command, function, or system call.
For those few man-pages pages in Sections 1 and 8,
probably you just want to write GNU.
For system calls, just write Linux. (An earlier practice
was to write the version number of the kernel from which
the manual page was being written/checked. However, this
was never done consistently, and so was probably worse
than including no version number. Henceforth, avoid
including a version number.)
For library calls that are part of glibc or one of the
other common GNU libraries, just use GNU C Library, GNU,
or an empty string.
For Section 4 pages, use Linux.
In cases of doubt, just write Linux, or GNU.
manual The title of the manual (e.g., for Section 2 and 3 pages
in the man-pages package, use Linux Programmer's Manual).
Sections within a manual page
The list below shows conventional or suggested sections. Most
manual pages should include at least the highlighted sections.
Arrange a new manual page so that sections are placed in the
order shown in the list.
NAME
SYNOPSIS
CONFIGURATION [Normally only in Section 4]
DESCRIPTION
OPTIONS [Normally only in Sections 1, 8]
EXIT STATUS [Normally only in Sections 1, 8]
RETURN VALUE [Normally only in Sections 2, 3]
ERRORS [Typically only in Sections 2, 3]
ENVIRONMENT
FILES
VERSIONS [Normally only in Sections 2, 3]
ATTRIBUTES [Normally only in Sections 2, 3]
CONFORMING TO
NOTES
BUGS
EXAMPLES
AUTHORS [Discouraged]
REPORTING BUGS [Not used in man-pages]
COPYRIGHT [Not used in man-pages]
SEE ALSO
Where a traditional heading would apply, please use it; this kind
of consistency can make the information easier to understand. If
you must, you can create your own headings if they make things
easier to understand (this can be especially useful for pages in
Sections 4 and 5). However, before doing this, consider whether
you could use the traditional headings, with some subsections
(.SS) within those sections.
The following list elaborates on the contents of each of the
above sections.
NAME The name of this manual page.
See man(7) for important details of the line(s) that
should follow the .SH NAME command. All words in this
line (including the word immediately following the "\-")
should be in lowercase, except where English or technical
terminological convention dictates otherwise.
SYNOPSIS
A brief summary of the command or function's interface.
For commands, this shows the syntax of the command and its
arguments (including options); boldface is used for as-is
text and italics are used to indicate replaceable
arguments. Brackets ([]) surround optional arguments,
vertical bars (|) separate choices, and ellipses (...) can
be repeated. For functions, it shows any required data
declarations or #include directives, followed by the
function declaration.
Where a feature test macro must be defined in order to
obtain the declaration of a function (or a variable) from
a header file, then the SYNOPSIS should indicate this, as
described in feature_test_macros(7).
CONFIGURATION
Configuration details for a device.
This section normally appears only in Section 4 pages.
DESCRIPTION
An explanation of what the program, function, or format
does.
Discuss how it interacts with files and standard input,
and what it produces on standard output or standard error.
Omit internals and implementation details unless they're
critical for understanding the interface. Describe the
usual case; for information on command-line options of a
program use the OPTIONS section.
When describing new behavior or new flags for a system
call or library function, be careful to note the kernel or
C library version that introduced the change. The
preferred method of noting this information for flags is
as part of a .TP list, in the following form (here, for a
new system call flag):
XYZ_FLAG (since Linux 3.7)
Description of flag...
Including version information is especially useful to
users who are constrained to using older kernel or C
library versions (which is typical in embedded systems,
for example).
OPTIONS
A description of the command-line options accepted by a
program and how they change its behavior.
This section should appear only for Section 1 and 8 manual
pages.
EXIT STATUS
A list of the possible exit status values of a program and
the conditions that cause these values to be returned.
This section should appear only for Section 1 and 8 manual
pages.
RETURN VALUE
For Section 2 and 3 pages, this section gives a list of
the values the library routine will return to the caller
and the conditions that cause these values to be returned.
ERRORS For Section 2 and 3 manual pages, this is a list of the
values that may be placed in errno in the event of an
error, along with information about the cause of the
errors.
Where several different conditions produce the same error,
the preferred approach is to create separate list entries
(with duplicate error names) for each of the conditions.
This makes the separate conditions clear, may make the
list easier to read, and allows metainformation (e.g.,
kernel version number where the condition first became
applicable) to be more easily marked for each condition.
The error list should be in alphabetical order.
ENVIRONMENT
A list of all environment variables that affect the
program or function and how they affect it.
FILES A list of the files the program or function uses, such as
configuration files, startup files, and files the program
directly operates on.
Give the full pathname of these files, and use the
installation process to modify the directory part to match
user preferences. For many programs, the default
installation location is in /usr/local, so your base
manual page should use /usr/local as the base.
ATTRIBUTES
A summary of various attributes of the function(s)
documented on this page. See attributes(7) for further
details.
VERSIONS
A brief summary of the Linux kernel or glibc versions
where a system call or library function appeared, or
changed significantly in its operation.
As a general rule, every new interface should include a
VERSIONS section in its manual page. Unfortunately, many
existing manual pages don't include this information
(since there was no policy to do so when they were
written). Patches to remedy this are welcome, but, from
the perspective of programmers writing new code, this
information probably matters only in the case of kernel
interfaces that have been added in Linux 2.4 or later
(i.e., changes since kernel 2.2), and library functions
that have been added to glibc since version 2.1 (i.e.,
changes since glibc 2.0).
The syscalls(2) manual page also provides information
about kernel versions in which various system calls first
appeared.
CONFORMING TO
A description of any standards or conventions that relate
to the function or command described by the manual page.
The preferred terms to use for the various standards are
listed as headings in standards(7).
For a page in Section 2 or 3, this section should note the
POSIX.1 version(s) that the call conforms to, and also
whether the call is specified in C99. (Don't worry too
much about other standards like SUS, SUSv2, and XPG, or
the SVr4 and 4.xBSD implementation standards, unless the
call was specified in those standards, but isn't in the
current version of POSIX.1.)
If the call is not governed by any standards but commonly
exists on other systems, note them. If the call is Linux-
specific, note this.
If this section consists of just a list of standards
(which it commonly does), terminate the list with a period
('.').
NOTES Miscellaneous notes.
For Section 2 and 3 man pages you may find it useful to
include subsections (SS) named Linux Notes and Glibc
Notes.
In Section 2, use the heading C library/kernel differences
to mark off notes that describe the differences (if any)
between the C library wrapper function for a system call
and the raw system call interface provided by the kernel.
BUGS A list of limitations, known defects or inconveniences,
and other questionable activities.
EXAMPLES
One or more examples demonstrating how this function,
file, or command is used.
For details on writing example programs, see Example
programs below.
AUTHORS
A list of authors of the documentation or program.
Use of an AUTHORS section is strongly discouraged.
Generally, it is better not to clutter every page with a
list of (over time potentially numerous) authors; if you
write or significantly amend a page, add a copyright
notice as a comment in the source file. If you are the
author of a device driver and want to include an address
for reporting bugs, place this under the BUGS section.
REPORTING BUGS
The man-pages project doesn't use a REPORTING BUGS section
in manual pages. Information on reporting bugs is instead
supplied in the script-generated COLOPHON section.
However, various projects do use a REPORTING BUGS section.
It is recommended to place it near the foot of the page.
COPYRIGHT
The man-pages project doesn't use a COPYRIGHT section in
manual pages. Copyright information is instead maintained
in the page source. In pages where this section is
present, it is recommended to place it near the foot of
the page, just above SEE ALSO.
SEE ALSO
A comma-separated list of related man pages, possibly
followed by other related pages or documents.
The list should be ordered by section number and then
alphabetically by name. Do not terminate this list with a
period.
Where the SEE ALSO list contains many long manual page
names, to improve the visual result of the output, it may
be useful to employ the .ad l (don't right justify) and
.nh (don't hyphenate) directives. Hyphenation of
individual page names can be prevented by preceding words
with the string "\%".
Given the distributed, autonomous nature of FOSS projects
and their documentation, it is sometimes necessary—and in
many cases desirable—that the SEE ALSO section includes
references to manual pages provided by other projects.
