The following subsections note some details for preferred formatting and wording conventions in various sections of the pages in the man-pages project.

SYNOPSIS

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 .P) may be added in the following cases:

• to separate long lists of function prototypes into related groups (see for example list(3));

• in other cases that may improve readability.

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:

1. If there is a single such prototype that needs to be continued, then align the continuation line so that when the page is rendered on a fixed-width font device (e.g., on an xterm) the continuation line starts just below the start of the argument list in the line above. (Exception: the indentation may be adjusted if necessary to prevent a very long continuation line or a further continuation line where the function prototype is very long.) As an example:

   int tcsetattr(int fd, int optional_actions,
    const struct termios *termios_p);

2. But, where multiple functions in the SYNOPSIS require continuation lines, and the function names have different lengths, then align all continuation lines to start in the same column. This provides a nicer rendering in PDF output (because the SYNOPSIS uses a variable width font where spaces render narrower than most characters). As an example:

   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);

RETURN VALUE

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.

ATTRIBUTES

Note the following:

• Wrap the table in this section in a .ad l/.ad pair to disable text filling and a .nh/.hy pair to disable hyphenation.

• Ensure that the table occupies the full page width through the use of an lbx description for one of the columns (usually the first column, though in some cases the last column if it contains a lot of text).

• Make free use of T{/T} macro pairs to allow table cells to be broken over multiple lines (also bearing in mind that pages may sometimes be rendered to a width of less than 80 columns).

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.

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 commands

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.

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.)

Use semantic newlines

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.

Lists

There are different kinds of lists:

Tagged paragraphs

These are used for a list of tags and their descriptions. When the tags are constants (either macros or numbers) they are in bold. Use the .TP macro.

An example is this "Tagged paragraphs" subsection is itself.

Ordered lists

Elements are preceded by a number in parentheses (1), (2). These represent a set of steps that have an order.

When there are substeps, they will be numbered like (4.2).

Positional lists

Elements are preceded by a number (index) in square brackets [4], [5]. These represent fields in a set. The first index will be:

0

When it represents fields of a C data structure, to be consistent with arrays.

1

When it represents fields of a file, to be consistent with tools like cut(1).

Alternatives list

Elements are preceded by a letter in parentheses (a), (b). These represent a set of (normally) exclusive alternatives.

Bullet lists

Elements are preceded by bullet symbols (\[bu]). Anything that doesn't fit elsewhere is usually covered by this type of list.

Numbered notes

Not really a list, but the syntax is identical to "positional 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.

Formatting conventions (general)

Paragraphs should be separated by suitable markers (usually either .P 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.

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:

• American English tends to use the forms "backward", "upward", "toward", and so on rather than the British forms "backwards", "upwards", "towards", and so on.

• Opinions are divided on "acknowledgement" vs "acknowledgment". The latter is predominant, but not universal usage in American English. POSIX and the BSD license use the former spelling. In the Linux man-pages project, we use "acknowledgement".

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), format them using the .EX and .EE macros, and surround them with suitable paragraph markers (either .P or .IP). For example:

.P
.in +4n
.EX
int
main(int argc, char *argv[])
{
    return 0;
}
.EE
.in
.P

Preferred terms

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.

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.

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

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 byte

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.", "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.

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.

Generating optimal glyphs

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 provide better renderings on various targets other than ASCII terminals, notably in PDF and on Unicode/UTF-8-capable terminals.

• To generate glyphs that when copied from rendered pages will produce real minus signs when pasted into a terminal.

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.

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:

• Example programs should be written in C.

• An example program is necessary and useful only if it demonstrates something beyond what can easily be provided in a textual description of the interface. An example program that does nothing other than call an interface usually serves little purpose.

• Example programs should ideally be short (e.g., a good example can often be provided in less than 100 lines of code), though in some cases longer programs may be necessary to properly illustrate the use of an API.

• Expressive code is appreciated.

• Comments should included where helpful. Complete sentences in free-standing comments should be terminated by a period. Periods should generally be omitted in "tag" comments (i.e., comments that are placed on the same line of code); such comments are in any case typically brief phrases rather than complete sentences.

• Example programs should do error checking after system calls and library function calls.

• Example programs should be complete, and compile without warnings when compiled with cc -Wall.

• Where possible and appropriate, example programs should allow experimentation, by varying their behavior based on inputs (ideally from command-line arguments, or alternatively, via input read by the program).

• Example programs should be laid out according to Kernighan and Ritchie style, with 4-space indents. (Avoid the use of TAB characters in source code!) The following command can be used to format your source code to something close to the preferred style:

  indent -npro -kr -i4 -ts4 -sob -l72 -ss -nut -psl prog.c

• For consistency, all example programs should terminate using either of:

  exit(EXIT_SUCCESS);
  exit(EXIT_FAILURE);

  Avoid using the following forms to terminate a program:

  exit(0);
  exit(1);
  return n;

• If there is extensive explanatory text before the program source code, mark off the source code with a subsection heading Program source, as in:

  .SS Program source

  Always do this if the explanatory text includes a shell session log.

If you include a shell session log demonstrating the use of a program or other system feature:

• Place the session log above the source code listing.

• Indent the session log by four spaces.

• Boldface the user input text, to distinguish it from output produced by the system.

For some examples of what example programs should look like, see wait(2) and pipe(2).