Sections of the manual pages

The manual Sections are traditionally defined as follows:

Macro package

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.

Conventions for source file layout

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.

Title line

The first command in a man page should be a TH command:

where:

Sections within a manual page

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.

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.

Use of gender-neutral language

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.

Formatting conventions for manual pages describing functions

For manual pages that describe 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.

Formatting conventions for manual pages describing functions

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.)

Formatting conventions (general)

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

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.

When showing example shell sessions, user input should be formatted in bold, for example

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.

Spelling

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:

BSD version numbers

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.

Capitalization

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

Indentation of structure definitions, shell session logs, and so on

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).

Preferred terms

The following table lists some preferred terms to use in man pages, mainly to ensure consistency across pages.

See also the discussion Hyphenation of attributive compounds below.

Terms to avoid

The following table lists some terms to avoid using in man pages, along with some suggested alternatives, mainly to ensure consistency across pages.

Trademarks

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

NULL, NUL, null pointer, and null character

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".

Hyperlinks

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

Use of e.g., i.e., etc., a.k.a., and similar

In general, the use of abbreviations such as "e.g.", "i.e.", "etc.", "a.k.a." should be avoided, in favor of suitable full wordings ("for example", "that is", "and so on", "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.

Em-dashes

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.

Hyphenation of attributive compounds

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

Hyphenation with multi, non, pre, re, sub, and so on

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.

Real minus character

Where a real minus character is required (e.g., for numbers such as −1, 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.

Character constants

To produce single quotes that render well in both ASCII and UTF-8, use the following form for character constants in the man page source:

\(aqC\(aq

where C is the quoted character. This guideline applies also to character constants used in code examples.

Example programs and shell sessions

Manual pages may include example programs demonstrating how to use a system call or library function. However, note the following:

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).