man
SYNOPSIS
groff -Tascii -man file ...
groff -Tps -man file ...
man [section] title
DESCRIPTION
This manual page explains the groff tmac.an macro package
(often called the man macro package) and related conven
tions for creating manual (man) pages. This macro package
should be used by developers when writing or porting man
pages for Linux. It is fairly compatible with other ver
sions of this macro package, so porting man pages should
not be a major problem (exceptions include the NET-2 BSD
release, which uses a totally different macro package
called mdoc; see mdoc(7)).
Note that NET-2 BSD mdoc man pages can be used with groff
simply by specifying the -mdoc option instead of the -man
option. Using the -mandoc option is, however, recom
mended, since this will automatically detect which macro
package is in use.
PREAMBLE
The first command in a man page (after comment lines)
should be
.TH title section date source manual,
where:
title The title of the man page (e.g., MAN).
section The section number the man page should be
placed in (e.g., 7).
date The date of the last revision--remember
to change this every time a change is
made to the man page, since this is the
most general way of doing version con
trol.
source The source of the command.
For binaries, use something like: GNU,
NET-2, SLS Distribution, MCC Distribu
tion.
For system calls, use the version of the
kernel that you are currently looking at:
Linux 0.99.11.
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 Macro packages and conventions
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 docu
mentation that exists is outdated
already. There are better sources of
information for kernel developers.
SECTIONS
Sections are started with .SH followed by the heading
name. If the name contains spaces and appears on the same
line as .SH, then place the heading in double quotes.
Traditional or suggested headings include: NAME, SYNOPSIS,
DESCRIPTION, RETURN VALUE, EXIT STATUS, ERROR HANDLING,
ERRORS, OPTIONS, USAGE, EXAMPLES, FILES, ENVIRONMENT,
DIAGNOSTICS, SECURITY, CONFORMING TO, NOTES, BUGS, AUTHOR,
and SEE ALSO. Where a traditional heading would apply,
please use it; this kind of consistency can make the
information easier to understand. However, feel free to
create your own headings if they make things easier to
understand. The only required heading is NAME, which
should be the first section and be followed on the next
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 ([]) sur
round 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 decla
ration.
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 stan
dard error. Omit internals and implementa
tion 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 subcom
mands, consider describing them in a sepa
rate USAGE section (and just place an
overview in the DESCRIPTION section).
RETURN VALUE gives a list of the values the library rou
tine will return to the caller and the con
ditions 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 pro
gram 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 oper
ates on. Give the full pathname of these
files, and use the installation process to
modify the directory part to match user
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, espe
cially if they aren't obvious. Discussing
security in a separate section isn't neces
sary; 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 inconve
niences, and other questionable activities.
AUTHOR lists authors of the documentation or pro
gram 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
Although there are many arbitrary conventions for man
pages in the UNIX world, the existence of several hundred
Linux-specific man pages defines our font standards:
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 sec
tion, 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 sub
.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 ens or
ems as units for indents, since these will automatically
adjust to font size changes. The other key macro defini
tions 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
graph's lines are indented).
.IP x i Indented paragraph with optional hanging tag. If
the tag x is omitted, the entire following para
graph is indented by i. If the tag x is pro
vided, 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 sim
plifies 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
.UR u Begins a hypertext link to the URI (URL) u; it
will end with the corresponding UE command. When
generating HTML this should translate into the
HTML command <A HREF="u">. There is an excep
tion: if u is the special value ":", then no
hypertext link of any kind will be generated
until after the closing UE (this permits dis
abling hypertext links in phrases like LALR(1)
when linking is not appropriate). These hyper
text link "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.
.UE Ends the corresponding UR command; when generat
ing HTML this should translate into </A>.
.UN u Creates a named hypertext location named u; do
not include a corresponding UE command. When
generating HTML this should translate into the
HTML command <A NAME="u" id="u"> </A> (the
is optional if support for Mosaic is
unneeded).
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
\*(lq Left angled doublequote: "
\*(rq Right angled doublequote: "
SAFE SUBSET
Although technically man is a troff macro package, in
reality a large number of other tools process man page
files that don't implement all of troff's abilities.
Thus, it's best to avoid some of troff's more exotic abil
ities where possible to permit these other tools to work
correctly. Avoid using the various troff preprocessors
(if you must, go ahead and use tbl(1), but try to use the
IP and TP commands instead for two-column tables). Avoid
using computations; most other tools can't process them.
Use simple commands that are easy to translate to other
formats. The following troff macros are believed to be
safe (though in many cases they will be ignored by trans
lators): \", ., ad, bp, br, ce, de, ds, el, ie, if, fi,
ft, hy, ig, in, na, ne, nf, nh, ps, so, sp, ti, tr.
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 neg
ative 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
list of characters, indicating how the page is to be pre
processed. For portability's sake to non-troff transla
tors 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
/usr/share/groff/[*/]tmac/tmac.an
/usr/man/whatis
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 consis
tent 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
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