| man-pages(7) | Miscellaneous Information Manual | man-pages(7) |
man-pages - conventions for writing Linux man pages
man [section] title
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, many of the pages that appear in Sections 3, 4, and 7, and a few of the pages that appear in Sections 1, 5, and 8 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:
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.
The first command in a man page should be a TH command:
The arguments of the command are as follows:
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.
| NAME | |
| LIBRARY | [Normally only in Sections 2, 3] |
| SYNOPSIS | |
| CONFIGURATION | [Normally only in Section 4] |
| DESCRIPTION | |
| 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] |
| ENVIRONMENT | |
| FILES | |
| ATTRIBUTES | [Normally only in Sections 2, 3] |
| VERSIONS | [Normally only in Sections 2, 3] |
| STANDARDS | |
| HISTORY | |
| NOTES | |
| CAVEATS | |
| BUGS | |
| EXAMPLES | |
| AUTHORS | [Discouraged] |
| REPORTING BUGS | [Not used in man-pages] |
| COPYRIGHT | [Not used in man-pages] |
| 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.
Old versions of standards should be mentioned here, rather than in STANDARDS, for example, SUS, SUSv2, and XPG, or the SVr4 and 4.xBSD implementation standards.
The following subsections note some details for preferred formatting and wording conventions in various sections of the pages in the man-pages project.
Wrap the function prototype(s) in a .nf/.fi pair to prevent filling.
In general, where more than one function prototype is shown in the SYNOPSIS, the prototypes should not be separated by blank lines. However, blank lines (achieved using .PP) may be added in the following cases:
In the SYNOPSIS, a long function prototype may need to be continued over to the next line. The continuation line is indented according to the following rules:
int tcsetattr(int fd, int optional_actions,
const struct termios *termios_p);
int getopt(int argc, char * const argv[],
const char *optstring);
int getopt_long(int argc, char * const argv[],
const char *optstring,
const struct option *longopts, int *longindex);
The preferred wording to describe how errno is set is "errno is set to indicate the error" or similar. This wording is consistent with the wording used in both POSIX.1 and FreeBSD.
Note the following:
For examples of all of the above, see the source code of various pages.
The following subsections describe the preferred style for the man-pages project. For details not covered below, the Chicago Manual of Style is usually a good source; try also grepping for preexisting usage in the project source tree.
As far as possible, use gender-neutral language in the text of man pages. Use of "they" ("them", "themself", "their") as a gender-neutral singular pronoun is acceptable.
For manual pages that describe a command (typically in Sections 1 and 8), the arguments are always specified using italics, even in the SYNOPSIS section.
The name of the command, and its options, should always be formatted in bold.
For manual pages that describe functions (typically in Sections 2 and 3), 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.
Any reference to the subject of the current manual page should be written with the name in bold 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.)
In the source of a manual page, new sentences should be started on new lines, long sentences should be split into lines at clause breaks (commas, semicolons, colons, and so on), and long clauses should be split at phrase boundaries. This convention, sometimes known as "semantic newlines", makes it easier to see the effect of patches, which often operate at the level of individual sentences, clauses, or phrases.
There are different kinds of lists:
There should always be exactly 2 spaces between the list symbol and the elements. This doesn't apply to "tagged paragraphs", which use the default indentation rules.
Paragraphs should be separated by suitable markers (usually either .PP or .IP). Do not separate paragraphs using blank lines, as this results in poor rendering in some output formats (such as PostScript and PDF).
Filenames (whether pathnames, or references to header files) 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 header file include, specify the header file surrounded by angle brackets, in the usual C way (e.g., <stdio.h>).
Special macros, which are usually in uppercase, 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 an indented line on their own, with a blank line before and after the command, 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 (\[ti]) 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.
When showing example shell sessions, user input should be formatted in bold, for example
$ date Thu Jul 7 13:01:27 CEST 2016
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.)
Control characters should be written in bold face, with no quotes; for example, ^X.
Starting with release 2.59, man-pages follows American spelling conventions (previously, there was a random mix of British and American spellings); please write all new pages and patches according to these conventions.
Aside from the well-known spelling differences, there are a few other subtleties to watch for:
The classical scheme for writing BSD version numbers is x.yBSD, where x.y is the version number (e.g., 4.2BSD). Avoid forms such as BSD 4.3.
In subsection ("SS") headings, capitalize the first word in the heading, but otherwise use lowercase, except where English usage (e.g., proper nouns) or programming language requirements (e.g., identifier names) dictate otherwise. For example:
.SS Unicode under Linux
When structure definitions, shell session logs, and so on are included in running text, indent them by 4 spaces (i.e., a block enclosed by .in +4n and .in), format them using the .EX and .EE macros, and surround them with suitable paragraph markers (either .PP or .IP). For example:
.PP
.in +4n
.EX
int
main(int argc, char *argv[])
{
return 0;
}
.EE
.in
.PP
The following table lists some preferred terms to use in man pages, mainly to ensure consistency across pages.
| Term | Avoid using | Notes |
| bit mask | bitmask | |
| built-in | builtin | |
| Epoch | epoch | For the UNIX Epoch (00:00:00, 1 Jan 1970 UTC) |
| filename | file name | |
| filesystem | file system | |
| hostname | host name | |
| inode | i-node | |
| lowercase | lower case, lower-case | |
| nonzero | non-zero | |
| pathname | path name | |
| pseudoterminal | pseudo-terminal | |
| privileged port | reserved port, system port | |
| real-time | realtime, real time | |
| run time | runtime | |
| saved set-group-ID | saved group ID, saved set-GID | |
| saved set-user-ID | saved user ID, saved set-UID | |
| set-group-ID | set-GID, setgid | |
| set-user-ID | set-UID, setuid | |
| superuser | super user, super-user | |
| superblock | super block, super-block | |
| symbolic link | symlink | |
| timestamp | time stamp | |
| timezone | time zone | |
| uppercase | upper case, upper-case | |
| usable | useable | |
| user space | userspace | |
| username | user name | |
| x86-64 | x86_64 | Except if referring to result of "uname -m" or similar |
| zeros | zeroes |
See also the discussion Hyphenation of attributive compounds below.
The following table lists some terms to avoid using in man pages, along with some suggested alternatives, mainly to ensure consistency across pages.
| Avoid | Use instead | Notes |
| 32bit | 32-bit | same for 8-bit, 16-bit, etc. |
| current process | calling process | A common mistake made by kernel programmers when writing man pages |
| manpage | man page, manual page | |
| minus infinity | negative infinity | |
| non-root | unprivileged user | |
| non-superuser | unprivileged user | |
| nonprivileged | unprivileged | |
| OS | operating system | |
| plus infinity | positive infinity | |
| pty | pseudoterminal | |
| tty | terminal | |
| Unices | UNIX systems | |
| Unixes | UNIX systems |
Use the correct spelling and case for trademarks. The following is a list of the correct spellings of various relevant trademarks that are sometimes misspelled:
| DG/UX |
| HP-UX |
| UNIX |
| UnixWare |
A null pointer is a pointer that points to nothing, and is normally indicated by the constant NULL. On the other hand, NUL is the null byte, a byte with the value 0, represented in C via the character constant '\0'.
The preferred term for the pointer is "null pointer" or simply "NULL"; avoid writing "NULL pointer".
The preferred term for the byte is "null byte". Avoid writing "NUL", since it is too easily confused with "NULL". Avoid also the terms "zero byte" and "null character". The byte that terminates a C string should be described as "the terminating null byte"; strings may be described as "null-terminated", but avoid the use of "NUL-terminated".
For hyperlinks, use the .UR/.UE macro pair (see groff_man(7)). This produces proper hyperlinks that can be used in a web browser, when rendering a page with, say:
BROWSER=firefox man -H pagename
In general, the use of abbreviations such as "e.g.", "i.e.", "etc.", "cf.", and "a.k.a." should be avoided, in favor of suitable full wordings ("for example", "that is", "and so on", "compare to", "also known as").
The only place where such abbreviations may be acceptable is in short parenthetical asides (e.g., like this one).
Always include periods in such abbreviations, as shown here. In addition, "e.g." and "i.e." should always be followed by a comma.
The way to write an em-dash—the glyph that appears at either end of this subphrase—in *roff is with the macro "\[em]". (On an ASCII terminal, an em-dash typically renders as two hyphens, but in other typographical contexts it renders as a long dash.) Em-dashes should be written without surrounding spaces.
Compound terms should be hyphenated when used attributively (i.e., to qualify a following noun). Some examples:
| 32-bit value |
| command-line argument |
| floating-point number |
| run-time check |
| user-space function |
| wide-character string |
The general tendency in modern English is not to hyphenate after prefixes such as "multi", "non", "pre", "re", "sub", and so on. Manual pages should generally follow this rule when these prefixes are used in natural English constructions with simple suffixes. The following list gives some examples of the preferred forms:
| interprocess |
| multithreaded |
| multiprocess |
| nonblocking |
| nondefault |
| nonempty |
| noninteractive |
| nonnegative |
| nonportable |
| nonzero |
| preallocated |
| precreate |
| prerecorded |
| reestablished |
| reinitialize |
| rearm |
| reread |
| subcomponent |
| subdirectory |
| subsystem |
Hyphens should be retained when the prefixes are used in nonstandard English words, with trademarks, proper nouns, acronyms, or compound terms. Some examples:
| non-ASCII |
| non-English |
| non-NULL |
| non-real-time |
Finally, note that "re-create" and "recreate" are two different verbs, and the former is probably what you want.
Where a real minus character is required (e.g., for numbers such as -1, for man page cross references such as utf-8(7), or when writing options that have a leading dash, such as in ls -l), use the following form in the man page source:
\-
This guideline applies also to code examples.
The use of real minus signs serves the following purposes:
To produce unslanted single quotes that render well in ASCII, UTF-8, and PDF, use "\[aq]" ("apostrophe quote"); for example
\[aq]C\[aq]
where C is the quoted character. This guideline applies also to character constants used in code examples.
Where a proper caret (^) that renders well in both a terminal and PDF is required, use "\[ha]". This is especially necessary in code samples, to get a nicely rendered caret when rendering to PDF.
Using a naked "~" character results in a poor rendering in PDF. Instead use "\[ti]". This is especially necessary in code samples, to get a nicely rendered tilde when rendering to PDF.
Manual pages may include example programs demonstrating how to use a system call or library function. However, note the following:
indent -npro -kr -i4 -ts4 -sob -l72 -ss -nut -psl prog.c
exit(EXIT_SUCCESS);
exit(EXIT_FAILURE);
exit(0);
exit(1);
return n;
.SS Program source
If you include a shell session log demonstrating the use of a program or other system feature:
For some examples of what example programs should look like, see wait(2) and pipe(2).
For canonical examples of how man pages in the man-pages package should look, see pipe(2) and fcntl(2).
man(1), man2html(1), attributes(7), groff(7), groff_man(7), man(7), mdoc(7)
| 2023-03-30 | Linux man-pages 6.05.01 |