1MAN-PAGES(7) Linux Programmer's Manual MAN-PAGES(7)
2
6 man-pages - conventions for writing Linux man pages
7
9 man [section] title
10
12 This page describes the conventions that should be employed when writ‐
13 ing man pages for the Linux man-pages project, which documents the
14 user-space API provided by the Linux kernel and the GNU C library. The
15 project thus provides most of the pages in Section 2, as well as many
16 of the pages that appear in Sections 3, 4, 5, and 7 of the man pages on
17 a Linux system. The conventions described on this page may also be
18 useful for authors writing man pages for other projects.
19 Sections of the manual pages
21 The manual Sections are traditionally defined as follows:
22 1 Commands (Programs)
24 Those commands that can be executed by the user from within a
25 shell.
26 2 System calls
28 Those functions which must be performed by the kernel.
29 3 Library calls
31 Most of the libc functions.
32 4 Special files (devices)
34 Files found in /dev.
35 5 File formats and conventions
37 The format for /etc/passwd and other human-readable files.
38 6 Games
40 7 Overview, conventions, and miscellaneous
42 Overviews of various topics, conventions and protocols, char‐
43 acter set standards, and miscellaneous other things.
44 8 System management commands
46 Commands like mount(8), many of which only root can execute.
47 Macro package
49 New manual pages should be marked up using the groff an.tmac package
50 described in man(7). This choice is mainly for consistency: the vast
51 majority of existing Linux manual pages are marked up using these
52 macros.
53 Conventions for source file layout
55 Please limit source code line length to no more than about 75 charac‐
56 ters wherever possible. This helps avoid line-wrapping in some mail
57 clients when patches are submitted inline.
58 New sentences should be started on new lines. This makes it easier to
60 see the effect of patches, which often operate at the level of individ‐
61 ual sentences.
62 Title line
64 The first command in a man page should be a TH command:
65 .TH title section date source manual
67 where:
69 title The title of the man page, written in all caps (e.g.,
71 MAN-PAGES).
72 section The section number in which the man page should be
74 placed (e.g., 7).
75 date The date of the last revision—remember to change this
77 every time a change is made to the man page, since
78 this is the most general way of doing version control.
79 Dates should be written in the form YYYY-MM-DD.
80 source The source of the command, function, or system call.
82 For those few man-pages pages in Sections 1 and 8,
84 probably you just want to write GNU.
85 For system calls, just write Linux. (An earlier prac‐
87 tice was to write the version number of the kernel
88 from which the manual page was being written/checked.
89 However, this was never done consistently, and so was
90 probably worse than including no version number.
91 Henceforth, avoid including a version number.)
92 For library calls that are part of glibc or one of the
94 other common GNU libraries, just use GNU C Library,
95 GNU, or an empty string.
96 For Section 4 pages, use Linux.
98 In cases of doubt, just write Linux, or GNU.
100 manual The title of the manual (e.g., for Section 2 and 3
102 pages in the man-pages package, use Linux Programmer's
103 Manual).
104 Sections within a manual page
106 The list below shows conventional or suggested sections. Most manual
107 pages should include at least the highlighted sections. Arrange a new
108 manual page so that sections are placed in the order shown in the list.
109 NAME
111 SYNOPSIS
112 CONFIGURATION [Normally only in Section 4]
113 DESCRIPTION
114 OPTIONS [Normally only in Sections 1, 8]
115 EXIT STATUS [Normally only in Sections 1, 8]
116 RETURN VALUE [Normally only in Sections 2, 3]
117 ERRORS [Typically only in Sections 2, 3]
118 ENVIRONMENT
119 FILES
120 ATTRIBUTES [Normally only in Sections 2, 3]
121 VERSIONS [Normally only in Sections 2, 3]
122 CONFORMING TO
123 NOTES
124 BUGS
125 EXAMPLE
126 SEE ALSO
127 Where a traditional heading would apply, please use it; this kind of
129 consistency can make the information easier to understand. If you
130 must, you can create your own headings if they make things easier to
131 understand (this can be especially useful for pages in Sections 4 and
132 5). However, before doing this, consider whether you could use the
133 traditional headings, with some subsections (.SS) within those sec‐
134 tions.
135 The following list elaborates on the contents of each of the above sec‐
137 tions.
138 NAME The name of this manual page. See man(7) for important
140 details of the line(s) that should follow the .SH NAME
141 command. All words in this line (including the word
142 immediately following the "\-") should be in lowercase,
143 except where English or technical terminological conven‐
144 tion dictates otherwise.
145 SYNOPSIS briefly describes the command or function's interface.
147 For commands, this shows the syntax of the command and
148 its arguments (including options); boldface is used for
149 as-is text and italics are used to indicate replaceable
150 arguments. Brackets ([]) surround optional arguments,
151 vertical bars (|) separate choices, and ellipses (...)
152 can be repeated. For functions, it shows any required
153 data declarations or #include directives, followed by the
154 function declaration.
155 Where a feature test macro must be defined in order to
157 obtain the declaration of a function (or a variable) from
158 a header file, then the SYNOPSIS should indicate this, as
159 described in feature_test_macros(7).
160 CONFIGURATION Configuration details for a device. This section nor‐
162 mally appears only in Section 4 pages.
163 DESCRIPTION gives an explanation of what the program, function, or
165 format does. Discuss how it interacts with files and
166 standard input, and what it produces on standard output
167 or standard error. Omit internals and implementation
168 details unless they're critical for understanding the
169 interface. Describe the usual case; for information on
170 command-line options of a program use the OPTIONS sec‐
171 tion.
172 When describing new behavior or new flags for a system
174 call or library function, be careful to note the kernel
175 or C library version that introduced the change. The
176 preferred method of noting this information for flags is
177 as part of a .TP list, in the following form (here, for a
178 new system call flag):
179 XYZ_FLAG (since Linux 3.7)
181 Description of flag...
182 Including version information is especially useful to
184 users who are constrained to using older kernel or C
185 library versions (which is typical in embedded systems,
186 for example).
187 OPTIONS describes the command-line options accepted by a program
189 and how they change its behavior. This section should
190 appear only for Section 1 and 8 manual pages.
191 EXIT STATUS lists the possible exit status values of a program and
193 the conditions that cause these values to be returned.
194 This section should appear only for Section 1 and 8 man‐
195 ual pages.
196 RETURN VALUE For Section 2 and 3 pages, this section gives a list of
198 the values the library routine will return to the caller
199 and the conditions that cause these values to be
200 returned.
201 ERRORS For Section 2 and 3 manual pages, this is a list of the
203 values that may be placed in errno in the event of an
204 error, along with information about the cause of the
205 errors. The error list should be in alphabetical order.
206 ENVIRONMENT lists all environment variables that affect the program
208 or function and how they affect it.
209 FILES lists the files the program or function uses, such as
211 configuration files, startup files, and files the program
212 directly operates on. Give the full pathname of these
213 files, and use the installation process to modify the
214 directory part to match user preferences. For many pro‐
215 grams, the default installation location is in
216 /usr/local, so your base manual page should use
217 /usr/local as the base.
218 ATTRIBUTES A summary of various attributes of the function(s) docu‐
220 mented on this page, broken into subsections. The fol‐
221 lowing subsections are defined:
222 Multithreading (see pthreads(7))
225 This subsection notes attributes relating to mul‐
226 tithreaded applications:
227 * Whether the function is thread-safe.
229 * Whether the function is a cancellation point.
231 * Whether the function is async-cancel-safe.
233 Details of these attributes can be found in
235 pthreads(7).
236 VERSIONS A brief summary of the Linux kernel or glibc versions
238 where a system call or library function appeared, or
239 changed significantly in its operation. As a general
240 rule, every new interface should include a VERSIONS sec‐
241 tion in its manual page. Unfortunately, many existing
242 manual pages don't include this information (since there
243 was no policy to do so when they were written). Patches
244 to remedy this are welcome, but, from the perspective of
245 programmers writing new code, this information probably
246 matters only in the case of kernel interfaces that have
247 been added in Linux 2.4 or later (i.e., changes since
248 kernel 2.2), and library functions that have been added
249 to glibc since version 2.1 (i.e., changes since glibc
250 2.0).
251 The syscalls(2) manual page also provides information
253 about kernel versions in which various system calls first
254 appeared.
255 CONFORMING TO describes any standards or conventions that relate to the
257 function or command described by the manual page. For a
258 page in Section 2 or 3, this section should note the
259 POSIX.1 version(s) that the call conforms to, and also
260 whether the call is specified in C99. (Don't worry too
261 much about other standards like SUS, SUSv2, and XPG, or
262 the SVr4 and 4.xBSD implementation standards, unless the
263 call was specified in those standards, but isn't in the
264 current version of POSIX.1.) (See standards(7).)
265 If the call is not governed by any standards but commonly
267 exists on other systems, note them. If the call is
268 Linux-specific, note this.
269 If this section consists of just a list of standards
271 (which it commonly does), terminate the list with a
272 period ('.').
273 NOTES provides miscellaneous notes. For Section 2 and 3 man
275 pages you may find it useful to include subsections (SS)
276 named Linux Notes and Glibc Notes.
277 BUGS lists limitations, known defects or inconveniences, and
279 other questionable activities.
280 EXAMPLE provides one or more examples describing how this func‐
282 tion, file or command is used. For details on writing
283 example programs, see Example Programs below.
284 AUTHORS lists authors of the documentation or program. Use of an
286 AUTHORS section is strongly discouraged. Generally, it
287 is better not to clutter every page with a list of (over
288 time potentially numerous) authors; if you write or sig‐
289 nificantly amend a page, add a copyright notice as a com‐
290 ment in the source file. If you are the author of a
291 device driver and want to include an address for report‐
292 ing bugs, place this under the BUGS section.
293 SEE ALSO provides a comma-separated list of related man pages,
295 ordered by section number and then alphabetically by
296 name, possibly followed by other related pages or docu‐
297 ments. Do not terminate this with a period.
298 Where the SEE ALSO list contains many long manual page
300 names, to improve the visual result of the output, it may
301 be useful to employ the .ad l (don't right justify) and
302 .nh (don't hyphenate) directives. Hyphenation of indi‐
303 vidual page names can be prevented by preceding words
304 with the string "\%".
305 Font conventions
307 For functions, the arguments are always specified using italics, even
308 in the SYNOPSIS section, where the rest of the function is specified in
309 bold:
310 int myfunction(int argc, char **argv);
312 Variable names should, like argument names, be specified in italics.
314 Filenames (whether pathnames, or references to files in the
316 /usr/include directory) are always in italics (e.g., <stdio.h>), except
317 in the SYNOPSIS section, where included files are in bold (e.g.,
318 #include <stdio.h>). When referring to a standard include file under
319 /usr/include, specify the header file surrounded by angle brackets, in
320 the usual C way (e.g., <stdio.h>).
321 Special macros, which are usually in upper case, are in bold (e.g.,
323 MAXINT). Exception: don't boldface NULL.
324 When enumerating a list of error codes, the codes are in bold (this
326 list usually uses the .TP macro).
327 Complete commands should, if long, be written as in an indented line on
329 their own, for example
330 man 7 man-pages
332 If the command is short, then it can be included inline in the text, in
334 italic format, for example, man 7 man-pages. In this case, it may be
335 worth using nonbreaking spaces ("\ ") at suitable places in the com‐
336 mand. Command options should be written in italics, e.g., -l.
337 Expressions, if not written on a separate indented line, should be
339 specified in italics. Again, the use of nonbreaking spaces may be
340 appropriate if the expression is inlined with normal text.
341 Any reference to the subject of the current manual page should be writ‐
343 ten with the name in bold. If the subject is a function (i.e., this is
344 a Section 2 or 3 page), then the name should be followed by a pair of
345 parentheses in Roman (normal) font. For example, in the fcntl(2) man
346 page, references to the subject of the page would be written as:
347 fcntl(). The preferred way to write this in the source file is:
348 .BR fcntl ()
350 (Using this format, rather than the use of "\fB...\fP()" makes it eas‐
352 ier to write tools that parse man page source files.)
353 Any reference to another man page should be written with the name in
355 bold, always followed by the section number, formatted in Roman (nor‐
356 mal) font, without any separating spaces (e.g., intro(2)). The pre‐
357 ferred way to write this in the source file is:
358 .BR intro (2)
360 (Including the section number in cross references lets tools like
362 man2html(1) create properly hyperlinked pages.)
363 Spelling
365 Starting with release 2.59, man-pages follows American spelling conven‐
366 tions; please write all new pages and patches according to these con‐
367 ventions.
368 Capitalization
370 In subsection ("SS") headings capitalize the first word in heading, but
371 otherwise use lower case, except where English usage (e.g., proper
372 nouns) or programming language requirements (e.g., identifier names)
373 dictate otherwise.
374 Example programs and shell sessions
376 Manual pages can include example programs demonstrating how to use a
377 system call or library function. However, note the following:
378 * Example programs should be written in C.
380 * An example program is necessary and useful only if it demonstrates
382 something beyond what can easily be provided in a textual descrip‐
383 tion of the interface. An example program that does nothing other
384 than call an interface usually serves little purpose.
385 * Example programs should be fairly short (preferably less than 100
387 lines; ideally less than 50 lines).
388 * Example programs should do error checking after system calls and
390 library function calls.
391 * Example programs should be complete, and compile without warnings
393 when compiled with cc -Wall.
394 * Where possible and appropriate, example programs should allow exper‐
396 imentation, by varying their behavior based on inputs (ideally from
397 command-line arguments, or alternatively, via input read by the pro‐
398 gram).
399 * Example programs should be laid out according to Kernighan and
401 Ritchie style, with 4-space indents. (Avoid the use of TAB charac‐
402 ters in source code!)
403 For some examples of what example programs should look like, see
405 wait(2) and pipe(2).
406 If you include a shell session demonstrating the use of a program or
408 other system feature, boldface the user input text, to distinguish it
409 from output produced by the system.
410 Indentation of structure definitions, shell session logs, etc.
412 When structure definitions, shell session logs, and so on are included
413 in running text, indent them by 4 spaces (i.e., a block enclosed by
414 .in +4n and .in).
415
417 For canonical examples of how man pages in the man-pages package should
418 look, see pipe(2) and fcntl(2).
419
421 man(1), man2html(1), groff(7), groff_man(7), man(7), mdoc(7)
422
424 This page is part of release 3.53 of the Linux man-pages project. A
425 description of the project, and information about reporting bugs, can
426 be found at http://www.kernel.org/doc/man-pages/.
427Linux 2013-07-24 MAN-PAGES(7)