Section: Linux Programmer's Manual (7)Updated: 2008-10-28Local indexUp
man-pages - conventions for writing Linux man pages
This page describes the conventions that should be employed
when writing man pages for the Linux man-pages project,
which comprises Sections 2, 3, 4, 5, and 7 of the Linux manual pages.
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
2 System calls
Those functions which must be performed by the kernel.
3 Library calls
Most of the
4 Special files (devices)
Files found in
5 File formats and conventions
The format for
and other human-readable files.
7 Conventions and miscellaneous
Overviews of various topics, conventions and protocols,
character set standards, and miscellaneous other things.
8 System management commands
many of which only root can execute.
New manual pages should be marked up using the
package described in
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
This helps avoid line-wrapping in some mail clients when patches are
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.
The first command in a man page should be a TH command:
.THtitle section date source manual
The title of the man page, written in all caps (e.g.,
The section number in which the man page should be placed (e.g.,
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.
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
For system calls, just write
(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
In cases of doubt, just write
Linux, or GNU.
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
Arrange a new manual page so that sections
are placed in the order shown in the list.
CONFIGURATION [Normally only in Section 4]
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]
VERSIONS [Normally only in Sections 2, 3]
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
The following list elaborates on the contents of each of
the above sections.
The name of this manual page.
for important details of the line(s) that should follow the
.SH NAME command.
briefly describes the command or function's interface.
For commands, this shows the syntax of the command and its arguments
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
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
Configuration details for a device.
This section normally only appears in Section 4 pages.
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
describes the command-line options accepted by a
program and how they change its behavior.
This section should only appear for Section 1 and 8 manual pages.
lists the possible exit status values of a program and
the conditions that cause these values to be returned.
This section should only appear for Section 1 and 8 manual pages.
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.
For Section 2 and 3 manual pages, this is a list of the
values that may be placed in
in the event of an error, along with information about the cause
of the errors.
The error list should be in alphabetical order.
lists all environment variables that affect the program or function
and how they affect it.
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
so your base manual page should use
as the base.
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.
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 only matters 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).
manual page also provides information about kernel versions
in which various system calls first appeared.
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.)
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 ('.').
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.
lists limitations, known defects or inconveniences,
and other questionable activities.
provides one or more examples describing how this function, file or
command is used.
For details on writing example programs,
see Example Programs below.
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.
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.
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
are always in italics (e.g.,
except in the SYNOPSIS section, where included files are in bold (e.g.,
When referring to a standard include file under
specify the header file surrounded by angle brackets,
in the usual C way (e.g.,
Special macros, which are usually in upper case, are in bold (e.g.,
Exception: don't boldface NULL.
When enumerating a list of error codes, the codes are in bold (this list
usually uses the
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.,
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
man page, references to the subject of the page would be written as:
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.,
The preferred way to write this in the source file is:
.BR intro (2)
(Including the section number in cross references lets tools like
create properly hyperlinked pages.)
Starting with release 2.59,
follows American spelling conventions;
please write all new pages and patches according to these conventions.
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 only necessary and useful 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
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, etc. are included
in running text, indent them by 4 spaces (i.e., a block enclosed by
For canonical examples of how man pages in the
package should look, see