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<standard input>:128: warning: table wider than line length minus indentation man‐pages(7) Miscellaneous Information Manual man‐pages(7)
NAME
man‐pages - conventions for writing Linux man pages
SYNOPSIS
man [section] title
DESCRIPTION
This page describes the conventions that should be em‐
ployed 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.
Sections of the manual pages
The manual Sections are traditionally defined as fol‐
lows:
1 User commands (Programs)
Commands that can be executed by the user from
within a shell.
2 System calls
Functions which wrap operations performed by the
kernel.
3 Library calls
All library functions excluding the system call
wrappers (Most of the libc functions).
4 Special files (devices)
Files found in /dev which allow to access to de‐
vices through the kernel.
5 File formats and configuration files
Describes various human‐readable file formats and
configuration files.
6 Games
Games and funny little programs available on the
system.
7 Overview, conventions, and miscellaneous
Overviews or descriptions of various topics, con‐
ventions, and protocols, character set standards,
the standard filesystem layout, and miscellaneous
other things.
8 System management commands
Commands like mount(8), many of which only root
can execute.
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 sub‐
mitted inline.
Title line
The first command in a man page should be a TH command:
.TH title section date source manual‐section
The arguments of the command are as follows:
title The title of the man page.
section
The section number in which the man page should
be placed (e.g., 7).
date The date of the last nontrivial change that was
made to the man page. (Within the man‐pages
project, the necessary updates to these time‐
stamps are handled automatically by scripts, so
there is no need to manually update them as part
of a patch.) Dates should be written in the form
YYYY‐MM‐DD.
source The name and version of the project that provides
the manual page (not necessarily the package that
provides the functionality).
manual‐section
Normally, this should be empty, since the default
value will be good.
Sections within a manual page
The list below shows conventional or suggested sections.
Most manual pages should include at least the high‐
lighted 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.
NAME The name of this manual page.
See man(7) for important details of the line(s)
that should follow the .SH NAME command. All
words in this line (including the word immedi‐
ately following the "\-") should be in lowercase,
except where English or technical terminological
convention dictates otherwise.
LIBRARY
The library providing a symbol.
It shows the common name of the library, and in
parentheses, the name of the library file and, if
needed, the linker flag needed to link a program
against it: (libfoo[, -lfoo]).
SYNOPSIS
A brief summary of the command or function’s in‐
terface.
For commands, this shows the syntax of the com‐
mand and its arguments (including options); bold‐
face is used for as‐is text and italics are used
to indicate replaceable arguments. Brackets ([])
surround optional arguments, vertical bars (|)
separate choices, and ellipses (...) can be re‐
peated. For functions, it shows any required
data declarations or #include directives, fol‐
lowed by the function declaration.
Where a feature test macro must be defined in or‐
der to obtain the declaration of a function (or a
variable) from a header file, then the SYNOPSIS
should indicate this, as described in fea‐
ture_test_macros(7).
CONFIGURATION
Configuration details for a device.
This section normally appears only in Section 4
pages.
DESCRIPTION
An explanation of what the program, function, or
format does.
Discuss how it interacts with files and standard
input, and what it produces on standard output or
standard error. Omit internals and implementa‐
tion details unless they’re critical for under‐
standing the interface. Describe the usual case;
for information on command‐line options of a pro‐
gram use the OPTIONS section.
When describing new behavior or new flags for a
system call or library function, be careful to
note the kernel or C library version that intro‐
duced the change. The preferred method of noting
this information for flags is as part of a .TP
list, in the following form (here, for a new sys‐
tem call flag):
XYZ_FLAG (since Linux 3.7)
Description of flag...
Including version information is especially use‐
ful to users who are constrained to using older
kernel or C library versions (which is typical in
embedded systems, for example).
OPTIONS
A description of the command‐line options ac‐
cepted by a program and how they change its be‐
havior.
This section should appear only for Section 1 and
8 manual pages.
EXIT STATUS
A list of the possible exit status values of a
program and the conditions that cause these val‐
ues to be returned.
This section should appear only for Section 1 and
8 manual pages.
RETURN VALUE
For Section 2 and 3 pages, this section gives a
list of the values the library routine will re‐
turn to the caller and the conditions that cause
these values to be returned.
ERRORS For Section 2 and 3 manual pages, this is a list
of the values that may be placed in errno in the
event of an error, along with information about
the cause of the errors.
Where several different conditions produce the
same error, the preferred approach is to create
separate list entries (with duplicate error
names) for each of the conditions. This makes
the separate conditions clear, may make the list
easier to read, and allows metainformation (e.g.,
kernel version number where the condition first
became applicable) to be more easily marked for
each condition.
The error list should be in alphabetical order.
ENVIRONMENT
A list of all environment variables that affect
the program or function and how they affect it.
FILES A list of the files the program or function uses,
such as configuration files, startup files, and
files the program directly operates on.
Give the full pathname of these files, and use
the installation process to modify the directory
part to match user preferences. For many pro‐
grams, the default installation location is in
/usr/local, so your base manual page should use
/usr/local as the base.
ATTRIBUTES
A summary of various attributes of the func‐
tion(s) documented on this page. See attrib‐
utes(7) for further details.
VERSIONS
A summary of systems where the API performs dif‐
ferently, or where there’s a similar API.
STANDARDS
A description of any standards or conventions
that relate to the function or command described
by the manual page.
The preferred terms to use for the various stan‐
dards are listed as headings in standards(7).
This section should note the current standards to
which the API conforms to.
If the API is not governed by any standards but
commonly exists on other systems, note them. If
the call is Linux‐specific or GNU‐specific, note
this. If it’s available in the BSDs, note that.
If this section consists of just a list of stan‐
dards (which it commonly does), terminate the
list with a period ('.').
HISTORY
A brief summary of the Linux kernel or glibc ver‐
sions where a system call or library function ap‐
peared, or changed significantly in its opera‐
tion.
As a general rule, every new interface should in‐
clude a HISTORY section in its manual page. Un‐
fortunately, many existing manual pages don’t in‐
clude this information (since there was no policy
to do so when they were written). Patches to
remedy this are welcome, but, from the perspec‐
tive of programmers writing new code, this infor‐
mation probably matters only in the case of ker‐
nel interfaces that have been added in Linux 2.4
or later (i.e., changes since Linux 2.2), and li‐
brary functions that have been added to glibc
since glibc 2.1 (i.e., changes since glibc 2.0).
The syscalls(2) manual page also provides infor‐
mation about kernel versions in which various
system calls first appeared.
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.
NOTES Miscellaneous notes.
For Section 2 and 3 man pages you may find it
useful to include subsections (SS) named
Linux Notes and glibc Notes.
In Section 2, use the heading C library/kernel
differences to mark off notes that describe the
differences (if any) between the C library wrap‐
per function for a system call and the raw system
call interface provided by the kernel.
CAVEATS
Warnings about typical user misuse of an API,
that don’t constitute an API bug or design de‐
fect.
BUGS A list of limitations, known defects or inconve‐
niences, and other questionable activities.
EXAMPLES
One or more examples demonstrating how this func‐
tion, file, or command is used.
For details on writing example programs, see Ex‐
ample programs below.
AUTHORS
A list of authors of the documentation or pro‐
gram.
Use of an AUTHORS section is strongly discouraged
. Generally, it is better not to clutter every
page with a list of (over time potentially numer‐
ous) authors; if you write or significantly amend
a page, add a copyright notice as a comment in
the source file. If you are the author of a de‐
vice driver and want to include an address for
reporting bugs, place this under the BUGS sec‐
tion.
REPORTING BUGS
The man‐pages project doesn’t use a REPORTING
BUGS section in manual pages. Information on re‐
porting bugs is instead supplied in the script‐
generated COLOPHON section. However, various
projects do use a REPORTING BUGS section. It is
recommended to place it near the foot of the
page.
COPYRIGHT
The man‐pages project doesn’t use a COPYRIGHT
section in manual pages. Copyright information
is instead maintained in the page source. In
pages where this section is present, it is recom‐
mended to place it near the foot of the page,
just above SEE ALSO.
SEE ALSO
A comma‐separated list of related man pages, pos‐
sibly followed by other related pages or docu‐
ments.
The list should be ordered by section number and
then alphabetically by name. Do not terminate
this list with a period.
Where the SEE ALSO list contains many long manual
page names, to improve the visual result of the
output, it may be useful to employ the <standard input>:851: warning: table wider than line length minus indentation
.ad l
(don’t right justify) and .nh (don’t hyphenate)
directives. Hyphenation of individual page names
can be prevented by preceding words with the
string "\%".
Given the distributed, autonomous nature of FOSS
projects and their documentation, it is sometimes
necessary—and in many cases desirable—that the
SEE ALSO section includes references to manual
pages provided by other projects.
FORMATTING AND WORDING CONVENTIONS
The following subsections note some details for pre‐
ferred 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 pre‐
vent filling.
In general, where more than one function prototype is
shown in the SYNOPSIS, the prototypes should not be sep‐
arated 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 indenta‐
tion 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 re‐
quire 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 nar‐
rower 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.
STYLE GUIDE
The following subsections describe the preferred style
for the man‐pages project. For details not covered be‐
low, 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 accept‐
able.
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 exam‐
ple, 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 "seman‐
tic 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 de‐
scriptions. 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 (usu‐
ally either .P or .IP). Do not separate paragraphs us‐
ing 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 in‐
dented 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 (\~) 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 non‐
breaking 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 "ac‐
knowledgment". 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 ex‐
ample:
.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 re‐
ferring to
result of
"uname -m" or
similar
zeros zeroes
See also the discussion Hyphenation of attributive com‐
pounds 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 accept‐
able 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 con‐
texts 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 attribu‐
tively (i.e., to qualify a following noun). Some exam‐
ples:
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 hyphen‐
ate 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 Eng‐
lish 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 num‐
bers 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 pur‐
poses:
• To provide better renderings on various targets other
than ASCII terminals, notably in PDF and on Uni‐
code/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 es‐
pecially necessary in code samples, to get a nicely ren‐
dered caret when rendering to PDF.
Using a naked "~" character results in a poor rendering
in PDF. Instead use "\[ti]". This is especially neces‐
sary 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 pro‐
vided 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 termi‐
nated by a period. Periods should generally be omit‐
ted 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 sys‐
tem 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 behav‐
ior based on inputs (ideally from command‐line argu‐
ments, or alternatively, via input read by the pro‐
gram).
• 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 termi‐
nate using either of:
exit(EXIT_SUCCESS);
exit(EXIT_FAILURE);
Avoid using the following forms to terminate a pro‐
gram:
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).
EXAMPLES
For canonical examples of how man pages in the man‐pages
package should look, see pipe(2) and fcntl(2).
SEE ALSO
man(1), man2html(1), attributes(7), groff(7),
groff_man(7), man(7), mdoc(7)
Linux man‐pages 6.14 2025‐05‐06 man‐pages(7)
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