Note that BSD mdoc-formatted pages begin with the Dd command, not the TH command.

The manual sections are traditionally defined as follows:

1 Commands

Those commands that can be executed by the user from within a shell.

2 System calls

Those functions which must be performed by the kernel.

3 Library calls

Most of the libc functions, such as qsort(3).

4 Special files

Files found in /dev.

5 File formats and conventions

The format for /etc/passwd and other human-readable files.

6 Games

7 Conventions and miscellaneous

A description of the standard file system layout, network protocols, ASCII and other character codes, this man page, and other things.

8 System management commands

Commands like mount(8), many of which only root can execute.

9 Kernel routines

This is an obsolete manual section. Once it was thought a good idea to document the Linux kernel here, but in fact very little has been documented, and the documentation that exists is outdated already. There are better sources of information for kernel developers.

SECTIONS 

.SH NAME chess \- the game of chess

Some other traditional sections have the following contents:

SYNOPSIS

briefly describes the command or function's interface. For commands, this shows the syntax of the command and its arguments (including options); boldface 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 repeated. For functions, it shows any required data declarations or #include directives, followed by the function declaration.

DESCRIPTION

gives an explanation of what the command, 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 implementation details unless they're critical for understanding the interface. Describe the usual case; for information on options use the OPTIONS section. If there is some kind of input grammar or complex set of subcommands, consider describing them in a separate USAGE section (and just place an overview in the DESCRIPTION section).

RETURN VALUE

gives a list of the values the library routine will return to the caller and the conditions that cause these values to be returned.

EXIT STATUS

lists the possible exit status values or a program and the conditions that cause these values to be returned.

OPTIONS

describes the options accepted by the program and how they change its behavior.

USAGE

describes the grammar of any sublanguage this implements.

EXAMPLES

provides one or more examples describing how this function, file or command is used.

FILES

lists 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 programs, the default installation location is in /usr/local, so your base manual page should use /usr/local as the base.

ENVIRONMENT

lists all environment variables that affect your program or function and how they affect it.

DIAGNOSTICS

gives an overview of the most common error messages and how to cope with them. You don't need to explain system error messages or fatal signals that can appear during execution of any program unless they're special in some way to your program.

SECURITY

discusses security issues and implications. Warn about configurations or environments that should be avoided, commands that may have security implications, and so on, especially if they aren't obvious. Discussing security in a separate section isn't necessary; if it's easier to understand, place security information in the other sections (such as the DESCRIPTION or USAGE section). However, please include security information somewhere!

CONFORMING TO

describes any standards or conventions this implements.

NOTES

provides miscellaneous notes.

BUGS

lists limitations, known defects or inconveniences, and other questionable activities.

AUTHOR

lists authors of the documentation or program so you can mail in bug reports.

SEE ALSO

lists related man pages in alphabetical order, possibly followed by other related pages or documents. Conventionally this is the last section.

FONTS 

For functions, 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);

Filenames are always in italics (e.g., /usr/include/stdio.h), except in the SYNOPSIS section, where included files are in bold (e.g., #include <stdio.h>).

Special macros, which are usually in upper case, are in bold (e.g., MAXINT).

When enumerating a list of error codes, the codes are in bold (this list usually uses the .TP macro).

Any reference to another man page (or to the subject of the current man page) is in bold. If the manual section number is given, it is given in Roman (normal) font, without any spaces (e.g., man(7)).

The commands to select the type face are:

.B

Bold

.BI

Bold alternating with italics (especially useful for function specifications)

.BR

Bold alternating with Roman (especially useful for referring to other manual pages)

.I

Italics

.IB

Italics alternating with bold

.IR

Italics alternating with Roman

.RB

Roman alternating with bold

.RI

Roman alternating with italics

.SB

Small alternating with bold

.SM

Small (useful for acronyms)

Traditionally, each command can have up to six arguments, but the GNU implementation removes this limitation (you might still want to limit yourself to 6 arguments for portability's sake). Arguments are delimited by spaces. Double quotes can be used to specify an argument which contains spaces. All of the arguments will be printed next to each other without intervening spaces, so that the .BR command can be used to specify a word in bold followed by a mark of punctuation in Roman. If no arguments are given, the command is applied to the following line of text.

OTHER MACROS AND STRINGS 

Below are other relevant macros and predefined strings. Unless noted otherwise, all macros cause a break (end the current line of text). Many of these macros set or use the "prevailing indent." The "prevailing indent" value is set by any macro with the parameter i below; macros may omit i in which case the current prevailing indent will be used. As a result, successive indented paragraphs can use the same indent without re-specifying the indent value. A normal (non-indented) paragraph resets the prevailing indent value to its default value (0.5 inches). By default a given indent is measured in ens; try to use ens or ems as units for indents, since these will automatically adjust to font size changes. The other key macro definitions are:

Normal Paragraphs 

.LP

Same as .PP (begin a new paragraph).

.P

Same as .PP (begin a new paragraph).

.PP

Begin a new paragraph and reset prevailing indent.

Relative Margin Indent 

.RS i

Start relative margin indent: moves the left margin i to the right (if i is omitted, the prevailing indent value is used). A new prevailing indent is set to 0.5 inches. As a result, all following paragraph(s) will be indented until the corresponding .RE.

.RE

End relative margin indent and restores the previous value of the prevailing indent.

Indented Paragraph Macros 

.HP i

Begin paragraph with a hanging indent (the first line of the paragraph is at the left margin of normal paragraphs, and the rest of the paragraph's lines are indented).

.IP x i

Indented paragraph with optional hanging tag. If the tag x is omitted, the entire following paragraph is indented by i. If the tag x is provided, it is hung at the left margin before the following indented paragraph (this is just like .TP except the tag is included with the command instead of being on the following line). If the tag is too long, the text after the tag will be moved down to the next line (text will not be lost or garbled). For bulleted lists, use this macro with \(bu (bullet) or \(em (em dash) as the tag, and for numbered lists, use the number or letter followed by a period as the tag; this simplifies translation to other formats.

.TP i

Begin paragraph with hanging tag. The tag is given on the next line, but its results are like those of the .IP command.

Hypertext Link Macros 

.URL url link trailer

Inserts a hypertext link to the URI (URL) url, with link as the text of the link. The trailer will be printed immediately afterwards. When generating HTML this should translate into the HTML command <A HREF="url">link</A>trailer.

This and other related macros are new, and many tools won't do anything with them, but since many tools (including troff) will simply ignore undefined macros (or at worst insert their text) these are safe to insert.

It can be useful to define your own URL macro in manual pages for the benefit of those viewing it with a roff viewer other than groff. That way, the URL, link text, and trailer text (if any) are still visible.

Here's an example:

.de URL \\$2 \(laURL: \\$1 \(ra\\$3 .. .if \n[.g] .mso www.tmac .TH ... (later in the page) This software comes from the .URL "http://www.gnu.org/" "GNU Project" " of the" .URL "http://www.fsf.org/" "Free Software Foundation" .

In the above, if groff is being used, the www.tmac macro package's definition of the URL macro will supersede the locally defined one.

A number of other link macros are available. See groff_www(7) for more details.

Miscellaneous Macros 

.DT

Reset tabs to default tab values (every 0.5 inches); does not cause a break.

.PD d

Set inter-paragraph vertical distance to d (if omitted, d=0.4v); does not cause a break.

.SS t

Subheading t (like .SH, but used for a subsection inside a section).

Predefined Strings 

\*R

Registration Symbol: ®

\*S

Change to default font size

\*(Tm

Trademark Symbol:

\*(lq

Left angled doublequote: ``

\*(rq

Right angled doublequote: ''

SAFE SUBSET 

You may also use many troff escape sequences (those sequences beginning with \). When you need to include the backslash character as normal text, use \e. Other sequences you may use, where x or xx are any characters and N is any digit, include: \', \`, \-, \., \ , \%, \*x, \*(xx, \(xx, \$N, \nx, \n(xx, \fx, and \f(xx. Avoid using the escape sequences for drawing graphics.

Do not use the optional parameter for bp (break page). Use only positive values for sp (vertical space). Don't define a macro (de) with the same name as a macro in this or the mdoc macro package with a different meaning; it's likely that such redefinitions will be ignored. Every positive indent (in) should be paired with a matching negative indent (although you should be using the RS and RE macros instead). The condition test (if,ie) should only have 't' or 'n' as the condition. Only translations (tr) that can be ignored should be used. Font changes (ft and the \f escape sequence) should only have the values 1, 2, 3, 4, R, I, B, P, or CW (the ft command may also have no parameters).

If you use capabilities beyond these, check the results carefully on several tools. Once you've confirmed that the additional capability is safe, let the maintainer of this document know about the safe command or sequence that should be added to this list.

NOTES 

By all means include full URLs (or URIs) in the text itself; some tools such as man2html(1) can automatically turn them into hypertext links. You can also use the new URL macro to identify links to related information. If you include URLs, use the full URL (e.g., <http://www.kernelnotes.org>) to ensure that tools can automatically find the URLs.

Tools processing these files should open the file and examine the first non-whitespace character. A period (.) or single quote (') at the beginning of a line indicates a troff-based file (such as man or mdoc). A left angle bracket (<) indicates an SGML/XML-based file (such as HTML or Docbook). Anything else suggests simple ASCII text (e.g., a "catman" result).

Many man pages begin with '\" followed by a space and a list of characters, indicating how the page is to be preprocessed. For portability's sake to non-troff translators we recommend that you avoid using anything other than tbl(1), and Linux can detect that automatically. However, you might want to include this information so your man page can be handled by other (less capable) systems. Here are the definitions of the preprocessors invoked by these characters:

e

eqn(1)

g

grap(1)

p

pic(1)

r

refer(1)

t

tbl(1)

v

vgrind(1)

FILES 

BUGS 

Most of the macros describe formatting (e.g., font type and spacing) instead of marking semantic content (e.g., this text is a reference to another page), compared to formats like mdoc and DocBook (even HTML has more semantic markings). This situation makes it harder to vary the man format for different media, to make the formatting consistent for a given media, and to automatically insert cross-references. By sticking to the safe subset described above, it should be easier to automate transitioning to a different reference page format in the future.

The Sun macro TX is not implemented.

AUTHORS 

---

James Clark (jjc@jclark.com) wrote the implementation of the macro package.

---

Rickard E. Faith (faith@cs.unc.edu) wrote the initial version of this manual page.

---

Jens Schweikhardt (schweikh@noc.fdn.de) wrote the Linux Man-Page Mini-HOWTO (which influenced this manual page).

---

David A. Wheeler (dwheeler@ida.org) heavily modified this manual page, such as adding detailed information on sections and macros.