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, many of the pages
16 that appear in Sections 3, 4, and 7, and a few of the pages that appear
17 in Sections 1, 5, and 8 of the man pages on a Linux system. The con‐
18 ventions described on this page may also be useful for authors writing
19 man pages for other projects.
20 Sections of the manual pages
22 The manual Sections are traditionally defined as follows:
23 1 User commands (Programs)
25 Commands that can be executed by the user from within a shell.
26 2 System calls
28 Functions which wrap operations performed by the kernel.
29 3 Library calls
31 All library functions excluding the system call wrappers (Most
32 of the libc functions).
33 4 Special files (devices)
35 Files found in /dev which allow to access to devices through the
36 kernel.
37 5 File formats and configuration files
39 Describes various human-readable file formats and configuration
40 files.
41 6 Games
43 Games and funny little programs available on the system.
44 7 Overview, conventions, and miscellaneous
46 Overviews or descriptions of various topics, conventions and
47 protocols, character set standards, the standard filesystem lay‐
48 out, and miscellaneous other things.
49 8 System management commands
51 Commands like mount(8), many of which only root can execute.
52 Macro package
54 New manual pages should be marked up using the groff an.tmac package
55 described in man(7). This choice is mainly for consistency: the vast
56 majority of existing Linux manual pages are marked up using these
57 macros.
58 Conventions for source file layout
60 Please limit source code line length to no more than about 75 charac‐
61 ters wherever possible. This helps avoid line-wrapping in some mail
62 clients when patches are submitted inline.
63 Title line
65 The first command in a man page should be a TH command:
66 .TH title section date source manual
68 where:
70 title The title of the man page, written in all caps (e.g.,
72 MAN-PAGES).
73 section The section number in which the man page should be
75 placed (e.g., 7).
76 date The date of the last nontrivial change that was made
78 to the man page. (Within the man-pages project, the
79 necessary updates to these timestamps are handled
80 automatically by scripts, so there is no need to manu‐
81 ally update them as part of a patch.) Dates should be
82 written in the form YYYY-MM-DD.
83 source The source of the command, function, or system call.
85 For those few man-pages pages in Sections 1 and 8,
87 probably you just want to write GNU.
88 For system calls, just write Linux. (An earlier prac‐
90 tice was to write the version number of the kernel
91 from which the manual page was being written/checked.
92 However, this was never done consistently, and so was
93 probably worse than including no version number.
94 Henceforth, avoid including a version number.)
95 For library calls that are part of glibc or one of the
97 other common GNU libraries, just use GNU C Library,
98 GNU, or an empty string.
99 For Section 4 pages, use Linux.
101 In cases of doubt, just write Linux, or GNU.
103 manual The title of the manual (e.g., for Section 2 and 3
105 pages in the man-pages package, use Linux Programmer's
106 Manual).
107 Sections within a manual page
109 The list below shows conventional or suggested sections. Most manual
110 pages should include at least the highlighted sections. Arrange a new
111 manual page so that sections are placed in the order shown in the list.
112 NAME
114 SYNOPSIS
115 CONFIGURATION [Normally only in Section 4]
116 DESCRIPTION
117 OPTIONS [Normally only in Sections 1, 8]
118 EXIT STATUS [Normally only in Sections 1, 8]
119 RETURN VALUE [Normally only in Sections 2, 3]
120 ERRORS [Typically only in Sections 2, 3]
121 ENVIRONMENT
122 FILES
123 VERSIONS [Normally only in Sections 2, 3]
124 ATTRIBUTES [Normally only in Sections 2, 3]
125 CONFORMING TO
126 NOTES
127 BUGS
128 EXAMPLES
129 AUTHORS [Discouraged]
130 REPORTING BUGS [Not used in man-pages]
131 COPYRIGHT [Not used in man-pages]
132 SEE ALSO
133 Where a traditional heading would apply, please use it; this kind of
135 consistency can make the information easier to understand. If you
136 must, you can create your own headings if they make things easier to
137 understand (this can be especially useful for pages in Sections 4 and
138 5). However, before doing this, consider whether you could use the
139 traditional headings, with some subsections (.SS) within those sec‐
140 tions.
141 The following list elaborates on the contents of each of the above sec‐
143 tions.
144 NAME The name of this manual page.
146 See man(7) for important details of the line(s) that should fol‐
148 low the .SH NAME command. All words in this line (including the
149 word immediately following the "\-") should be in lowercase,
150 except where English or technical terminological convention dic‐
151 tates otherwise.
152 SYNOPSIS
154 A brief summary of the command or function's interface.
155 For commands, this shows the syntax of the command and its argu‐
157 ments (including options); boldface is used for as-is text and
158 italics are used to indicate replaceable arguments. Brackets
159 ([]) surround optional arguments, vertical bars (|) separate
160 choices, and ellipses (...) can be repeated. For functions, it
161 shows any required data declarations or #include directives,
162 followed by the function declaration.
163 Where a feature test macro must be defined in order to obtain
165 the declaration of a function (or a variable) from a header
166 file, then the SYNOPSIS should indicate this, as described in
167 feature_test_macros(7).
168 CONFIGURATION
170 Configuration details for a device.
171 This section normally appears only in Section 4 pages.
173 DESCRIPTION
175 An explanation of what the program, function, or format does.
176 Discuss how it interacts with files and standard input, and what
178 it produces on standard output or standard error. Omit inter‐
179 nals and implementation details unless they're critical for
180 understanding the interface. Describe the usual case; for
181 information on command-line options of a program use the OPTIONS
182 section.
183 When describing new behavior or new flags for a system call or
185 library function, be careful to note the kernel or C library
186 version that introduced the change. The preferred method of
187 noting this information for flags is as part of a .TP list, in
188 the following form (here, for a new system call flag):
189 XYZ_FLAG (since Linux 3.7)
191 Description of flag...
192 Including version information is especially useful to users who
194 are constrained to using older kernel or C library versions
195 (which is typical in embedded systems, for example).
196 OPTIONS
198 A description of the command-line options accepted by a program
199 and how they change its behavior.
200 This section should appear only for Section 1 and 8 manual
202 pages.
203 EXIT STATUS
205 A list of the possible exit status values of a program and the
206 conditions that cause these values to be returned.
207 This section should appear only for Section 1 and 8 manual
209 pages.
210 RETURN VALUE
212 For Section 2 and 3 pages, this section gives a list of the val‐
213 ues the library routine will return to the caller and the condi‐
214 tions that cause these values to be returned.
215 ERRORS For Section 2 and 3 manual pages, this is a list of the values
217 that may be placed in errno in the event of an error, along with
218 information about the cause of the errors.
219 Where several different conditions produce the same error, the
221 preferred approach is to create separate list entries (with
222 duplicate error names) for each of the conditions. This makes
223 the separate conditions clear, may make the list easier to read,
224 and allows metainformation (e.g., kernel version number where
225 the condition first became applicable) to be more easily marked
226 for each condition.
227 The error list should be in alphabetical order.
229 ENVIRONMENT
231 A list of all environment variables that affect the program or
232 function and how they affect it.
233 FILES A list of the files the program or function uses, such as con‐
235 figuration files, startup files, and files the program directly
236 operates on.
237 Give the full pathname of these files, and use the installation
239 process to modify the directory part to match user preferences.
240 For many programs, the default installation location is in
241 /usr/local, so your base manual page should use /usr/local as
242 the base.
243 ATTRIBUTES
245 A summary of various attributes of the function(s) documented on
246 this page. See attributes(7) for further details.
247 VERSIONS
249 A brief summary of the Linux kernel or glibc versions where a
250 system call or library function appeared, or changed signifi‐
251 cantly in its operation.
252 As a general rule, every new interface should include a VERSIONS
254 section in its manual page. Unfortunately, many existing manual
255 pages don't include this information (since there was no policy
256 to do so when they were written). Patches to remedy this are
257 welcome, but, from the perspective of programmers writing new
258 code, this information probably matters only in the case of ker‐
259 nel interfaces that have been added in Linux 2.4 or later (i.e.,
260 changes since kernel 2.2), and library functions that have been
261 added to glibc since version 2.1 (i.e., changes since glibc
262 2.0).
263 The syscalls(2) manual page also provides information about ker‐
265 nel versions in which various system calls first appeared.
266 CONFORMING TO
268 A description of any standards or conventions that relate to the
269 function or command described by the manual page.
270 The preferred terms to use for the various standards are listed
272 as headings in standards(7).
273 For a page in Section 2 or 3, this section should note the
275 POSIX.1 version(s) that the call conforms to, and also whether
276 the call is specified in C99. (Don't worry too much about other
277 standards like SUS, SUSv2, and XPG, or the SVr4 and 4.xBSD
278 implementation standards, unless the call was specified in those
279 standards, but isn't in the current version of POSIX.1.)
280 If the call is not governed by any standards but commonly exists
282 on other systems, note them. If the call is Linux-specific,
283 note this.
284 If this section consists of just a list of standards (which it
286 commonly does), terminate the list with a period ('.').
287 NOTES Miscellaneous notes.
289 For Section 2 and 3 man pages you may find it useful to include
291 subsections (SS) named Linux Notes and Glibc Notes.
292 In Section 2, use the heading C library/kernel differences to
294 mark off notes that describe the differences (if any) between
295 the C library wrapper function for a system call and the raw
296 system call interface provided by the kernel.
297 BUGS A list of limitations, known defects or inconveniences, and
299 other questionable activities.
300 EXAMPLES
302 One or more examples demonstrating how this function, file or
303 command is used.
304 For details on writing example programs, see Example programs
306 below.
307 AUTHORS
309 A list of authors of the documentation or program.
310 Use of an AUTHORS section is strongly discouraged. Generally,
312 it is better not to clutter every page with a list of (over time
313 potentially numerous) authors; if you write or significantly
314 amend a page, add a copyright notice as a comment in the source
315 file. If you are the author of a device driver and want to
316 include an address for reporting bugs, place this under the BUGS
317 section.
318 REPORTING BUGS
320 The man-pages project doesn't use a REPORTING BUGS section in
321 manual pages. Information on reporting bugs is instead supplied
322 in the script-generated COLOPHON section. However, various
323 projects do use a REPORTING BUGS section. it is recommended to
324 place it near the foot of the page.
325 COPYRIGHT
327 The man-pages project doesn't use a COPYRIGHT section in manual
328 pages. Copyright information is instead maintained in the page
329 source. In pages where this section is present, it is recom‐
330 mended to place it near the foot of the page, just above SEE
331 ALSO.
332 SEE ALSO
334 A comma-separated list of related man pages, possibly followed
335 by other related pages or documents.
336 The list should be ordered by section number and then alphabeti‐
338 cally by name. Do not terminate this list with a period.
339 Where the SEE ALSO list contains many long manual page names, to
341 improve the visual result of the output, it may be useful to
342 employ the .ad l (don't right justify) and .nh (don't hyphenate)
343 directives. Hyphenation of individual page names can be pre‐
344 vented by preceding words with the string "\%".
345 Given the distributed, autonomous nature of FOSS projects and
347 their documentation, it is sometimes necessary—and in many cases
348 desirable—that the SEE ALSO section includes references to man‐
349 ual pages provided by other projects.
350
352 The following subsections describe the preferred style for the man-
353 pages project. For details not covered below, the Chicago Manual of
354 Style is usually a good source; try also grepping for preexisting usage
355 in the project source tree.
356 Use of gender-neutral language
358 As far as possible, use gender-neutral language in the text of man
359 pages. Use of "they" ("them", "themself", "their") as a gender-neutral
360 singular pronoun is acceptable.
361 Formatting conventions for manual pages describing commands
363 For manual pages that describe a command (typically in Sections 1 and
364 8), the arguments are always specified using italics, even in the SYN‐
365 OPSIS section.
366 The name of the command, and its options, should always be formatted in
368 bold.
369 Formatting conventions for manual pages describing functions
371 For manual pages that describe functions (typically in Sections 2 and
372 3), the arguments are always specified using italics, even in the SYN‐
373 OPSIS section, where the rest of the function is specified in bold:
374 int myfunction(int argc, char **argv);
376 Variable names should, like argument names, be specified in italics.
378 Any reference to the subject of the current manual page should be writ‐
380 ten with the name in bold followed by a pair of parentheses in Roman
381 (normal) font. For example, in the fcntl(2) man page, references to
382 the subject of the page would be written as: fcntl(). The preferred
383 way to write this in the source file is:
384 .BR fcntl ()
386 (Using this format, rather than the use of "\fB...\fP()" makes it eas‐
388 ier to write tools that parse man page source files.)
389 Use semantic newlines
391 In the source of a manual page, new sentences should be started on new
392 lines, and long sentences should split into lines at clause breaks
393 (commas, semicolons, colons, and so on). This convention, sometimes
394 known as "semantic newlines", makes it easier to see the effect of
395 patches, which often operate at the level of individual sentences or
396 sentence clauses.
397 Formatting conventions (general)
399 Paragraphs should be separated by suitable markers (usually either .PP
400 or .IP). Do not separate paragraphs using blank lines, as this results
401 in poor rendering in some output formats (such as PostScript and PDF).
402 Filenames (whether pathnames, or references to header files) are always
404 in italics (e.g., <stdio.h>), except in the SYNOPSIS section, where
405 included files are in bold (e.g., #include <stdio.h>). When referring
406 to a standard header file include, specify the header file surrounded
407 by angle brackets, in the usual C way (e.g., <stdio.h>).
408 Special macros, which are usually in uppercase, are in bold (e.g., MAX‐
410 INT). Exception: don't boldface NULL.
411 When enumerating a list of error codes, the codes are in bold (this
413 list usually uses the .TP macro).
414 Complete commands should, if long, be written as an indented line on
416 their own, with a blank line before and after the command, for example
417 man 7 man-pages
419 If the command is short, then it can be included inline in the text, in
421 italic format, for example, man 7 man-pages. In this case, it may be
422 worth using nonbreaking spaces ("\ ") at suitable places in the com‐
423 mand. Command options should be written in italics (e.g., -l).
424 Expressions, if not written on a separate indented line, should be
426 specified in italics. Again, the use of nonbreaking spaces may be
427 appropriate if the expression is inlined with normal text.
428 When showing example shell sessions, user input should be formatted in
430 bold, for example
431 $ date
433 Thu Jul 7 13:01:27 CEST 2016
434 Any reference to another man page should be written with the name in
436 bold, always followed by the section number, formatted in Roman (nor‐
437 mal) font, without any separating spaces (e.g., intro(2)). The pre‐
438 ferred way to write this in the source file is:
439 .BR intro (2)
441 (Including the section number in cross references lets tools like
443 man2html(1) create properly hyperlinked pages.)
444 Control characters should be written in bold face, with no quotes; for
446 example, ^X.
447 Spelling
449 Starting with release 2.59, man-pages follows American spelling conven‐
450 tions (previously, there was a random mix of British and American
451 spellings); please write all new pages and patches according to these
452 conventions.
453 Aside from the well-known spelling differences, there are a few other
455 subtleties to watch for:
456 * American English tends to use the forms "backward", "upward",
458 "toward", and so on rather than the British forms "backwards",
459 "upwards", "towards", and so on.
460 BSD version numbers
462 The classical scheme for writing BSD version numbers is x.yBSD, where
463 x.y is the version number (e.g., 4.2BSD). Avoid forms such as BSD 4.3.
464 Capitalization
466 In subsection ("SS") headings, capitalize the first word in the head‐
467 ing, but otherwise use lowercase, except where English usage (e.g.,
468 proper nouns) or programming language requirements (e.g., identifier
469 names) dictate otherwise. For example:
470 .SS Unicode under Linux
472 Indentation of structure definitions, shell session logs, and so on
474 When structure definitions, shell session logs, and so on are included
475 in running text, indent them by 4 spaces (i.e., a block enclosed by
476 .in +4n and .in), format them using the .EX and EE macros, and surround
477 them with suitable paragraph markers (either .PP or .IP). For example:
478 .PP
480 .in +4n
481 .EX
482 int
483 main(int argc, char *argv[])
484 {
485 return 0;
486 }
487 .EE
488 .in
489 .PP
490 Preferred terms
492 The following table lists some preferred terms to use in man pages,
493 mainly to ensure consistency across pages.
494 Term Avoid using Notes
496 ──────────────────────────────────────────────────────────────────
497 bit mask bitmask
499 built-in builtin
500 Epoch epoch For the UNIX Epoch
501 (00:00:00, 1 Jan
502 1970 UTC)
503 filename file name
504 filesystem file system
505 hostname host name
506 inode i-node
507 lowercase lower case, lower-case
508 nonzero non-zero
509 pathname path name
510 pseudoterminal pseudo-terminal
511 privileged port reserved port, system
512 port
513 real-time realtime, real time
514 run time runtime
515 saved set-group-ID saved group ID, saved
516 set-GID
517 saved set-user-ID saved user ID, saved
518 set-UID
519 set-group-ID set-GID, setgid
520 set-user-ID set-UID, setuid
521 superuser super user, super-user
522 superblock super block, super-
523 block
524 timestamp time stamp
525 timezone time zone
526 uppercase upper case, upper-case
527 usable useable
528 user space userspace
529 username user name
530 x86-64 x86_64 Except if referring
531 to result of
532 "uname -m" or simi‐
533 lar
534 zeros zeroes
535 See also the discussion Hyphenation of attributive compounds below.
537 Terms to avoid
539 The following table lists some terms to avoid using in man pages, along
540 with some suggested alternatives, mainly to ensure consistency across
541 pages.
542 Avoid Use instead Notes
544 ────────────────────────────────────────────────────────────
545 32bit 32-bit same for 8-bit,
548 16-bit, etc.
549 current process calling process A common mistake
550 made by kernel pro‐
551 grammers when writ‐
552 ing man pages
553 manpage man page, manual
554 page
555 minus infinity negative infinity
556 non-root unprivileged user
557 non-superuser unprivileged user
558 nonprivileged unprivileged
559 OS operating system
560 plus infinity positive infinity
561 pty pseudoterminal
562 tty terminal
563 Unices UNIX systems
564 Unixes UNIX systems
565 Trademarks
567 Use the correct spelling and case for trademarks. The following is a
568 list of the correct spellings of various relevant trademarks that are
569 sometimes misspelled:
570 DG/UX
572 HP-UX
573 UNIX
574 UnixWare
575 NULL, NUL, null pointer, and null character
577 A null pointer is a pointer that points to nothing, and is normally
578 indicated by the constant NULL. On the other hand, NUL is the null
579 byte, a byte with the value 0, represented in C via the character con‐
580 stant '\0'.
581 The preferred term for the pointer is "null pointer" or simply "NULL";
583 avoid writing "NULL pointer".
584 The preferred term for the byte is "null byte". Avoid writing "NUL",
586 since it is too easily confused with "NULL". Avoid also the terms
587 "zero byte" and "null character". The byte that terminates a C string
588 should be described as "the terminating null byte"; strings may be
589 described as "null-terminated", but avoid the use of "NUL-terminated".
590 Hyperlinks
592 For hyperlinks, use the .UR/.UE macro pair (see groff_man(7)). This
593 produces proper hyperlinks that can be used in a web browser, when ren‐
594 dering a page with, say:
595 BROWSER=firefox man -H pagename
597 Use of e.g., i.e., etc., a.k.a., and similar
599 In general, the use of abbreviations such as "e.g.", "i.e.", "etc.",
600 "cf.", and "a.k.a." should be avoided, in favor of suitable full word‐
601 ings ("for example", "that is", "compare to", "and so on", "also known
602 as").
603 The only place where such abbreviations may be acceptable is in short
605 parenthetical asides (e.g., like this one).
606 Always include periods in such abbreviations, as shown here. In addi‐
608 tion, "e.g." and "i.e." should always be followed by a comma.
609 Em-dashes
611 The way to write an em-dash—the glyph that appears at either end of
612 this subphrase—in *roff is with the macro "\(em". (On an ASCII termi‐
613 nal, an em-dash typically renders as two hyphens, but in other typo‐
614 graphical contexts it renders as a long dash.) Em-dashes should be
615 written without surrounding spaces.
616 Hyphenation of attributive compounds
618 Compound terms should be hyphenated when used attributively (i.e., to
619 qualify a following noun). Some examples:
620 32-bit value
622 command-line argument
623 floating-point number
624 run-time check
625 user-space function
626 wide-character string
627 Hyphenation with multi, non, pre, re, sub, and so on
629 The general tendency in modern English is not to hyphenate after pre‐
630 fixes such as "multi", "non", "pre", "re", "sub", and so on. Manual
631 pages should generally follow this rule when these prefixes are used in
632 natural English constructions with simple suffixes. The following list
633 gives some examples of the preferred forms:
634 interprocess
636 multithreaded
637 multiprocess
638 nonblocking
639 nondefault
640 nonempty
641 noninteractive
642 nonnegative
643 nonportable
644 nonzero
645 preallocated
646 precreate
647 prerecorded
648 reestablished
649 reinitialize
650 rearm
651 reread
652 subcomponent
653 subdirectory
654 subsystem
655 Hyphens should be retained when the prefixes are used in nonstandard
657 English words, with trademarks, proper nouns, acronyms, or compound
658 terms. Some examples:
659 non-ASCII
661 non-English
662 non-NULL
663 non-real-time
664 Finally, note that "re-create" and "recreate" are two different verbs,
666 and the former is probably what you want.
667 Real minus character
669 Where a real minus character is required (e.g., for numbers such as -1,
670 for man page cross references such as utf-8(7), or when writing options
671 that have a leading dash, such as in ls -l), use the following form in
672 the man page source:
673 \-
675 This guideline applies also to code examples.
677 Character constants
679 To produce single quotes that render well in both ASCII and UTF-8, use
680 the following form for character constants in the man page source:
681 \(aqC\(aq
683 where C is the quoted character. This guideline applies also to char‐
685 acter constants used in code examples.
686 Example programs and shell sessions
688 Manual pages may include example programs demonstrating how to use a
689 system call or library function. However, note the following:
690 * Example programs should be written in C.
692 * An example program is necessary and useful only if it demonstrates
694 something beyond what can easily be provided in a textual descrip‐
695 tion of the interface. An example program that does nothing other
696 than call an interface usually serves little purpose.
697 * Example programs should be fairly short (preferably less than 100
699 lines; ideally less than 50 lines).
700 * Example programs should do error checking after system calls and
702 library function calls.
703 * Example programs should be complete, and compile without warnings
705 when compiled with cc -Wall.
706 * Where possible and appropriate, example programs should allow exper‐
708 imentation, by varying their behavior based on inputs (ideally from
709 command-line arguments, or alternatively, via input read by the pro‐
710 gram).
711 * Example programs should be laid out according to Kernighan and
713 Ritchie style, with 4-space indents. (Avoid the use of TAB charac‐
714 ters in source code!) The following command can be used to format
715 your source code to something close to the preferred style:
716 indent -npro -kr -i4 -ts4 -sob -l72 -ss -nut -psl prog.c
718 * For consistency, all example programs should terminate using either
720 of:
721 exit(EXIT_SUCCESS);
723 exit(EXIT_FAILURE);
724 Avoid using the following forms to terminate a program:
726 exit(0);
728 exit(1);
729 return n;
730 * If there is extensive explanatory text before the program source
732 code, mark off the source code with a subsection heading Program
733 source, as in:
734 .SS Program source
736 Always do this if the explanatory text includes a shell session log.
738 If you include a shell session log demonstrating the use of a program
740 or other system feature:
741 * Place the session log above the source code listing
743 * Indent the session log by four spaces.
745 * Boldface the user input text, to distinguish it from output produced
747 by the system.
748 For some examples of what example programs should look like, see
750 wait(2) and pipe(2).
751
753 For canonical examples of how man pages in the man-pages package should
754 look, see pipe(2) and fcntl(2).
755
757 man(1), man2html(1), attributes(7), groff(7), groff_man(7), man(7),
758 mdoc(7)
759
761 This page is part of release 5.07 of the Linux man-pages project. A
762 description of the project, information about reporting bugs, and the
763 latest version of this page, can be found at
764 https://www.kernel.org/doc/man-pages/.
765Linux 2020-04-11 MAN-PAGES(7)