|
|
man-pages — conventions for writing Linux man pages
man
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: System Calls, 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.
The manual Sections are traditionally defined as follows:
Those commands that can be executed by the user from within a shell.
Those functions which must be performed by the kernel.
Most of the libc functions.
Files found in /dev.
The format for /etc/passwd and other
human-readable files.
Overviews of various topics, conventions and protocols, character set standards, and miscellaneous other things.
Commands like mount(8), many of which only root can execute.
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.
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.
The first command in a man page should be a TH command:
.THtitle section date source manual
where:
titleThe title of the man page, written in all caps (e.g.,
MAN-PAGES).sectionThe section number in which the man page should be placed (e.g.,
7).dateThe 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.
sourceThe source of the command, function, or system call.
For those few
man-pagespages in Sections 1 and 8, probably you just want to writeGNU.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: Special Files pages, use
Linux.In cases of doubt, just write
Linux, orGNU.manualThe title of the manual (e.g., for Section 2: System Calls and 3 pages in the
man-pagespackage, use Linux Programmer's Manual).
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.
NAMESYNOPSISCONFIGURATION [Normally only in Section 4: Special Files]DESCRIPTIONOPTIONS [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.
NAMEThe 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.
SYNOPSISbriefly 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).
CONFIGURATIONConfiguration details for a device. This section normally appears only in Section 4: Special Files pages.
DESCRIPTIONgives 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).
OPTIONSdescribes the command-line options accepted by a program and how they change its behavior. This section should appear only for Section 1: General Commands and 8 manual pages.
EXITSTATUSlists 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.
RETURNVALUEFor Section 2: System Calls 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.
ERRORSFor Section 2: System Calls 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.
ENVIRONMENTlists all environment variables that affect the program or function and how they affect it.
FILESlists 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.
ATTRIBUTESA 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).
VERSIONSA 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.
CONFORMINGTOdescribes any standards or conventions that relate to the function or command described by the manual page. For a page in Section 2: System Calls 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 ('.').
NOTESprovides miscellaneous notes. For Section 2: System Calls and 3
man pages you may find it useful to include
subsections (SS) named
Linux Notes
and Glibc
Notes.
BUGSlists limitations, known defects or inconveniences, and other questionable activities.
EXAMPLEprovides one or more examples describing how this function, file or command is used. For details on writing example programs, see Example Programs below.
AUTHORSlists 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.
SEEALSOprovides 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
"\".
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: System Calls 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.)
Starting with release 2.59, man-pages follows American
spelling conventions; please write all new pages and
patches according to these conventions.
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.
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.
For canonical examples of how man pages in the man-pages package should
look, see pipe(2) and fcntl(2).
This page is part of release 3.53 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/.
|
(C) Copyright 1992-1999 Rickard E. Faith and David A. Wheeler (faithcs.unc.edu and dwheelerida.org) and (C) Copyright 2007 Michael Kerrisk <mtk.manpagesgmail.com> %%%LICENSE_START(VERBATIM) Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Since the Linux kernel and libraries are constantly changing, this manual page may be incorrect or out-of-date. The author(s) assume no responsibility for errors or omissions, or for damages resulting from the use of the information contained herein. The author(s) may not have taken the same level of care in the production of this manual, which is licensed free of charge, as they might when working professionally. Formatted or processed versions of this manual, if unaccompanied by the source, must acknowledge the copyright and authors of this work. %%%LICENSE_END 2007-05-30 created by mtk, using text from old man.7 plus rewrites and additional text. |