1MAN-PAGES(7) Linux Programmer's Manual MAN-PAGES(7)
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6 man-pages - conventions for writing Linux man pages
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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 comprises Sections
14 2, 3, 4, 5, and 7 of the Linux manual pages. The conventions described
15 on this page may also be useful for authors writing man pages for other
16 projects.
17 Sections of the Manual Pages
19 The manual Sections are traditionally defined as follows:
20 1 Commands (Programs)
22 Those commands that can be executed by the user from within a
23 shell.
24 2 System calls
26 Those functions which must be performed by the kernel.
27 3 Library calls
29 Most of the libc functions.
30 4 Special files (devices)
32 Files found in /dev.
33 5 File formats and conventions
35 The format for /etc/passwd and other human-readable files.
36 6 Games
38 7 Conventions and miscellaneous
40 Overviews of various topics, conventions and protocols, char‐
41 acter set standards, and miscellaneous other things.
42 8 System management commands
44 Commands like mount(8), many of which only root can execute.
45 Macro package
47 New manual pages should be marked up using the groff an.tmac package
48 described in man(7). This choice is mainly for consistency: the vast
49 majority of existing Linux manual pages are marked up using these
50 macros.
51 Conventions for source file layout
53 Please limit source code line length to no more than about 75 charac‐
54 ters wherever possible. This helps avoid line-wrapping in some mail
55 clients when patches are submitted inline.
56 New sentences should be started on new lines. This makes it easier to
58 see the effect of patches, which often operate at the level of individ‐
59 ual sentences.
60 Title line
62 The first command in a man page should be a TH command:
63 .TH title section date source manual
65 where:
67 title The title of the man page, written in all caps (e.g.,
69 MAN-PAGES).
70 section The section number in which the man page should be
72 placed (e.g., 7).
73 date The date of the last revision — remember to change
75 this every time a change is made to the man page,
76 since this is the most general way of doing version
77 control. Dates should be written in the form YYYY-MM-
78 DD.
79 source The source of the command, function, or system call.
81 For those few man-pages pages in Sections 1 and 8,
83 probably you just want to write GNU.
84 For system calls, just write Linux. (An earlier prac‐
86 tice was to write the version number of the kernel
87 from which the manual page was being written/checked.
88 However, this was never done consistently, and so was
89 probably worse than including no version number.
90 Henceforth, avoid including a version number.)
91 For library calls that are part of glibc or one of the
93 other common GNU libraries, just use GNU C Library,
94 GNU, or an empty string.
95 For Section 4 pages, use Linux.
97 In cases of doubt, just write Linux, or GNU.
99 manual The title of the manual (e.g., for Section 2 and 3
101 pages in the man-pages package, use Linux Programmer's
102 Manual).
103 Sections within a manual page
105 The list below shows conventional or suggested sections. Most manual
106 pages should include at least the highlighted sections. Arrange a new
107 manual page so that sections are placed in the order shown in the list.
108 NAME
110 SYNOPSIS
111 CONFIGURATION [Normally only in Section 4]
112 DESCRIPTION
113 OPTIONS [Normally only in Sections 1, 8]
114 EXIT STATUS [Normally only in Sections 1, 8]
115 RETURN VALUE [Normally only in Sections 2, 3]
116 ERRORS [Typically only in Sections 2, 3]
117 ENVIRONMENT
118 FILES
119 VERSIONS [Normally only in Sections 2, 3]
120 CONFORMING TO
121 NOTES
122 BUGS
123 EXAMPLE
124 SEE ALSO
125 Where a traditional heading would apply, please use it; this kind of
127 consistency can make the information easier to understand. If you
128 must, you can create your own headings if they make things easier to
129 understand (this can be especially useful for pages in Sections 4 and
130 5). However, before doing this, consider whether you could use the
131 traditional headings, with some subsections (.SS) within those sec‐
132 tions.
133 The following list elaborates on the contents of each of the above sec‐
135 tions.
136 NAME The name of this manual page. See man(7) for important
138 details of the line(s) that should follow the .SH NAME
139 command.
140 SYNOPSIS briefly describes the command or function's interface.
142 For commands, this shows the syntax of the command and
143 its arguments (including options); boldface is used for
144 as-is text and italics are used to indicate replaceable
145 arguments. Brackets ([]) surround optional arguments,
146 vertical bars (|) separate choices, and ellipses (...)
147 can be repeated. For functions, it shows any required
148 data declarations or #include directives, followed by the
149 function declaration.
150 Where a feature test macro must be defined in order to
152 obtain the declaration of a function (or a variable) from
153 a header file, then the SYNOPSIS should indicate this, as
154 described in feature_test_macros(7).
155 CONFIGURATION Configuration details for a device. This section nor‐
157 mally only appears in Section 4 pages.
158 DESCRIPTION gives an explanation of what the program, function, or
160 format does. Discuss how it interacts with files and
161 standard input, and what it produces on standard output
162 or standard error. Omit internals and implementation
163 details unless they're critical for understanding the
164 interface. Describe the usual case; for information on
165 command-line options of a program use the OPTIONS sec‐
166 tion.
167 OPTIONS describes the command-line options accepted by a program
169 and how they change its behavior. This section should
170 only appear for Section 1 and 8 manual pages.
171 EXIT STATUS lists the possible exit status values of a program and
173 the conditions that cause these values to be returned.
174 This section should only appear for Section 1 and 8 man‐
175 ual pages.
176 RETURN VALUE For Section 2 and 3 pages, this section gives a list of
178 the values the library routine will return to the caller
179 and the conditions that cause these values to be
180 returned.
181 ERRORS For Section 2 and 3 manual pages, this is a list of the
183 values that may be placed in errno in the event of an
184 error, along with information about the cause of the
185 errors. The error list should be in alphabetical order.
186 ENVIRONMENT lists all environment variables that affect the program
188 or function and how they affect it.
189 FILES lists the files the program or function uses, such as
191 configuration files, startup files, and files the program
192 directly operates on. Give the full pathname of these
193 files, and use the installation process to modify the
194 directory part to match user preferences. For many pro‐
195 grams, the default installation location is in
196 /usr/local, so your base manual page should use
197 /usr/local as the base.
198 VERSIONS A brief summary of the Linux kernel or glibc versions
200 where a system call or library function appeared, or
201 changed significantly in its operation. As a general
202 rule, every new interface should include a VERSIONS sec‐
203 tion in its manual page. Unfortunately, many existing
204 manual pages don't include this information (since there
205 was no policy to do so when they were written). Patches
206 to remedy this are welcome, but, from the perspective of
207 programmers writing new code, this information probably
208 only matters in the case of kernel interfaces that have
209 been added in Linux 2.4 or later (i.e., changes since
210 kernel 2.2), and library functions that have been added
211 to glibc since version 2.1 (i.e., changes since glibc
212 2.0).
213 The syscalls(2) manual page also provides information
215 about kernel versions in which various system calls first
216 appeared.
217 CONFORMING TO describes any standards or conventions that relate to the
219 function or command described by the manual page. For a
220 page in Section 2 or 3, this section should note the
221 POSIX.1 version(s) that the call conforms to, and also
222 whether the call is specified in C99. (Don't worry too
223 much about other standards like SUS, SUSv2, and XPG, or
224 the SVr4 and 4.xBSD implementation standards, unless the
225 call was specified in those standards, but isn't in the
226 current version of POSIX.1.) (See standards(7).)
227 If the call is not governed by any standards but commonly
229 exists on other systems, note them. If the call is
230 Linux-specific, note this.
231 If this section consists of just a list of standards
233 (which it commonly does), terminate the list with a
234 period ('.').
235 NOTES provides miscellaneous notes. For Section 2 and 3 man
237 pages you may find it useful to include subsections (SS)
238 named Linux Notes and Glibc Notes.
239 BUGS lists limitations, known defects or inconveniences, and
241 other questionable activities.
242 EXAMPLE provides one or more examples describing how this func‐
244 tion, file or command is used. For details on writing
245 example programs, see Example Programs below.
246 AUTHORS lists authors of the documentation or program. Use of an
248 AUTHORS section is strongly discouraged. Generally, it
249 is better not to clutter every page with a list of (over
250 time potentially numerous) authors; if you write or sig‐
251 nificantly amend a page, add a copyright notice as a com‐
252 ment in the source file. If you are the author of a
253 device driver and want to include an address for report‐
254 ing bugs, place this under the BUGS section.
255 SEE ALSO provides a comma-separated list of related man pages,
257 ordered by section number and then alphabetically by
258 name, possibly followed by other related pages or docu‐
259 ments. Do not terminate this with a period.
260 Font conventions
262 For functions, the arguments are always specified using italics, even
263 in the SYNOPSIS section, where the rest of the function is specified in
264 bold:
265 int myfunction(int argc, char **argv);
267 Variable names should, like argument names, be specified in italics.
269 Filenames (whether pathnames, or references to files in the
271 /usr/include directory) are always in italics (e.g., <stdio.h>), except
272 in the SYNOPSIS section, where included files are in bold (e.g.,
273 #include <stdio.h>). When referring to a standard include file under
274 /usr/include, specify the header file surrounded by angle brackets, in
275 the usual C way (e.g., <stdio.h>).
276 Special macros, which are usually in upper case, are in bold (e.g.,
278 MAXINT). Exception: don't boldface NULL.
279 When enumerating a list of error codes, the codes are in bold (this
281 list usually uses the .TP macro).
282 Complete commands should, if long, be written as in an indented line on
284 their own, for example
285 man 7 man-pages
287 If the command is short, then it can be included inline in the text, in
289 italic format, for example, man 7 man-pages. In this case, it may be
290 worth using nonbreaking spaces ("\ ") at suitable places in the com‐
291 mand. Command options should be written in italics, e.g., -l.
292 Expressions, if not written on a separate indented line, should be
294 specified in italics. Again, the use of nonbreaking spaces may be
295 appropriate if the expression is inlined with normal text.
296 Any reference to the subject of the current manual page should be writ‐
298 ten with the name in bold. If the subject is a function (i.e., this is
299 a Section 2 or 3 page), then the name should be followed by a pair of
300 parentheses in Roman (normal) font. For example, in the fcntl(2) man
301 page, references to the subject of the page would be written as:
302 fcntl(). The preferred way to write this in the source file is:
303 .BR fcntl ()
305 (Using this format, rather than the use of "\fB...\fP()" makes it eas‐
307 ier to write tools that parse man page source files.)
308 Any reference to another man page should be written with the name in
310 bold, always followed by the section number, formatted in Roman (nor‐
311 mal) font, without any separating spaces (e.g., intro(2)). The pre‐
312 ferred way to write this in the source file is:
313 .BR intro (2)
315 (Including the section number in cross references lets tools like
317 man2html(1) create properly hyperlinked pages.)
318 Spelling
320 Starting with release 2.59, man-pages follows American spelling conven‐
321 tions; please write all new pages and patches according to these con‐
322 ventions.
323 Example Programs and Shell Sessions
325 Manual pages can include example programs demonstrating how to use a
326 system call or library function. However, note the following:
327 * Example programs should be written in C.
329 * An example program is only necessary and useful if it demonstrates
331 something beyond what can easily be provided in a textual descrip‐
332 tion of the interface. An example program that does nothing other
333 than call an interface usually serves little purpose.
334 * Example programs should be fairly short (preferably less than 100
336 lines; ideally less than 50 lines).
337 * Example programs should do error checking after system calls and
339 library function calls.
340 * Example programs should be complete, and compile without warnings
342 when compiled with cc -Wall.
343 * Where possible and appropriate, example programs should allow exper‐
345 imentation, by varying their behavior based on inputs (ideally from
346 command-line arguments, or alternatively, via input read by the pro‐
347 gram).
348 * Example programs should be laid out according to Kernighan and
350 Ritchie style, with 4-space indents. (Avoid the use of TAB charac‐
351 ters in source code!)
352 For some examples of what example programs should look like, see
354 wait(2) and pipe(2).
355 If you include a shell session demonstrating the use of a program or
357 other system feature, boldface the user input text, to distinguish it
358 from output produced by the system.
359 Indentation of structure definitions, shell session logs, etc.
361 When structure definitions, shell session logs, etc. are included in
362 running text, indent them by 4 spaces (i.e., a block enclosed by
363 .in +4n and .in).
364
366 For canonical examples of how man pages in the man-pages package should
367 look, see pipe(2) and fcntl(2).
368
370 man(1), man2html(1), groff(7), groff_man(7), man(7), mdoc(7)
371
373 This page is part of release 3.25 of the Linux man-pages project. A
374 description of the project, and information about reporting bugs, can
375 be found at http://www.kernel.org/doc/man-pages/.
376Linux 2008-10-28 MAN-PAGES(7)