Provided by: manpages_3.54-1ubuntu1_all 
NAME
man-pages - conventions for writing Linux man pages
SYNOPSIS
man [section] title
DESCRIPTION
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, as well as many of the pages that appear in
Sections 3, 4, 5, and 7 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 Commands (Programs)
Those commands that can be executed by the user from within a shell.
2 System calls
Those functions which must be performed by the kernel.
3 Library calls
Most of the libc functions.
4 Special files (devices)
Files found in /dev.
5 File formats and conventions
The format for /etc/passwd and other human-readable files.
6 Games
7 Overview, conventions, and miscellaneous
Overviews of various topics, conventions and protocols, character set standards, 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.
New sentences should be started on new lines. This makes it easier to see the effect of patches, which
often operate at the level of individual sentences.
Title line
The first command in a man page should be a TH command:
.TH title section date source manual
where:
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 revision—remember to change this every time a change is made to the
man page, since this is the most general way of doing version control. 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
ATTRIBUTES [Normally only in Sections 2, 3]
VERSIONS [Normally only in Sections 2, 3]
CONFORMING TO
NOTES
BUGS
EXAMPLE
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 briefly describes 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 gives 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 describes 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 lists 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. The error
list should be in alphabetical order.
ENVIRONMENT lists all environment variables that affect the program or function and how they affect it.
FILES lists 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, broken into
subsections. The following subsections are defined:
Multithreading (see pthreads(7))
This subsection notes attributes relating to multithreaded applications:
* Whether the function is thread-safe.
* Whether the function is a cancellation point.
* Whether the function is async-cancel-safe.
Details of these attributes can be found in pthreads(7).
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 describes any standards or conventions that relate to the function or command described by
the manual page. 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.) (See standards(7).)
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 provides miscellaneous notes. For Section 2 and 3 man pages you may find it useful to
include subsections (SS) named Linux Notes and Glibc Notes.
BUGS lists limitations, known defects or inconveniences, and other questionable activities.
EXAMPLE provides one or more examples describing how this function, file or command is used. For
details on writing example programs, see Example Programs below.
AUTHORS lists 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.
SEE ALSO provides a comma-separated list of related man pages, ordered by section number and then
alphabetically by name, possibly followed by other related pages or documents. Do not
terminate this 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 "\%".
Font conventions
For functions, the arguments are always specified using italics, even in the SYNOPSIS section, where the
rest of the function is specified in bold:
int myfunction(int argc, char **argv);
Variable names should, like argument names, be specified in italics.
Filenames (whether pathnames, or references to files in the /usr/include directory) are always in italics
(e.g., <stdio.h>), except in the SYNOPSIS section, where included files are in bold (e.g., #include
<stdio.h>). When referring to a standard include file under /usr/include, specify the header file
surrounded by angle brackets, in the usual C way (e.g., <stdio.h>).
Special macros, which are usually in upper case, are in bold (e.g., MAXINT). Exception: don't boldface
NULL.
When enumerating a list of error codes, the codes are in bold (this list usually uses the .TP macro).
Complete commands should, if long, be written as in an indented line on their own, for example
man 7 man-pages
If the command is short, then it can be included inline in the text, in italic format, for example, man 7
man-pages. In this case, it may be worth using nonbreaking spaces ("\ ") at suitable places in the
command. Command options should be written in italics, e.g., -l.
Expressions, if not written on a separate indented line, should be specified in italics. Again, the use
of nonbreaking spaces may be appropriate if the expression is inlined with normal text.
Any reference to the subject of the current manual page should be written with the name in bold. If the
subject is a function (i.e., this is a Section 2 or 3 page), then the name should be followed by a pair
of parentheses in Roman (normal) font. For example, in the fcntl(2) man page, references to the subject
of the page would be written as: fcntl(). The preferred way to write this in the source file is:
.BR fcntl ()
(Using this format, rather than the use of "\fB...\fP()" makes it easier to write tools that parse man
page source files.)
Any reference to another man page should be written with the name in bold, always followed by the section
number, formatted in Roman (normal) font, without any separating spaces (e.g., intro(2)). The preferred
way to write this in the source file is:
.BR intro (2)
(Including the section number in cross references lets tools like man2html(1) create properly hyperlinked
pages.)
Spelling
Starting with release 2.59, man-pages follows American spelling conventions; please write all new pages
and patches according to these conventions.
Capitalization
In subsection ("SS") headings capitalize the first word in heading, but otherwise use lower case, except
where English usage (e.g., proper nouns) or programming language requirements (e.g., identifier names)
dictate otherwise.
Example programs and shell sessions
Manual pages can include example programs demonstrating how to use a system call or library function.
However, note the following:
* Example programs should be written in C.
* An example program is necessary and useful only if it demonstrates something beyond what can easily be
provided in a textual description of the interface. An example program that does nothing other than
call an interface usually serves little purpose.
* Example programs should be fairly short (preferably less than 100 lines; ideally less than 50 lines).
* Example programs should do error checking after system calls and library function calls.
* Example programs should be complete, and compile without warnings when compiled with cc -Wall.
* Where possible and appropriate, example programs should allow experimentation, by varying their
behavior based on inputs (ideally from command-line arguments, or alternatively, via input read by the
program).
* Example programs should be laid out according to Kernighan and Ritchie style, with 4-space indents.
(Avoid the use of TAB characters in source code!)
For some examples of what example programs should look like, see wait(2) and pipe(2).
If you include a shell session demonstrating the use of a program or other system feature, boldface the
user input text, to distinguish it from output produced by the system.
Indentation of structure definitions, shell session logs, etc.
When structure definitions, shell session logs, and so on are included in running text, indent them by 4
spaces (i.e., a block enclosed by .in +4n and .in).
EXAMPLE
For canonical examples of how man pages in the man-pages package should look, see pipe(2) and fcntl(2).
SEE ALSO
man(1), man2html(1), groff(7), groff_man(7), man(7), mdoc(7)
COLOPHON
This page is part of release 3.54 of the Linux man-pages project. A description of the project, and
information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.