Copyright 1995-2002 by Jens Schweikhardt, email: <howto at schweikhardt dot net>
See further information on copying conditions below.
$Id: man_page_howto.html,v 1.21 2003/01/06 16:31:07 schweikh Exp schweikh $
Click here to browse the author's latest version of this document. Corrections and suggestions welcome!
This HOWTO explains what you should bear in mind when you are going
to write on-line documentation -- a so-called man page -- that you want
to make accessible via the man(1) command. Throughout this
HOWTO, a manual entry is simply referred to as a man page, regardless of
actual length and without sexist intention.
apropos and whatis to work?1) A few thoughts on documentation
Why do we write documentation? Silly question. Because we want others to be able to use our program, library function or whatever we have written and made available. But writing documentation is not all there is to it:
The historical and well known way documentation is accessed on UNIX
is via the man(1) command. This HOWTO describes what you have to do to
write a man page that will be correctly processed by the documentation-
related tools. The most important of these tools are man(1), xman(1x),
apropos(1), makewhatis(8) and catman(8). Reliability and accuracy of the
information are, of course, up to you. But even in this respect you will
find some ideas below that help you avoid some common
glitches.
2) How are man pages accessed?
You need to know the precise mechanism for acccessing man pages in order to give your man page the right name and install it in the right place. Each man page should be categorized in a specific section, denoted by a single character. The most common sections under Linux, and their human readable names, are:
Section The human readable name 1 User commands that may be started by everyone. 2 System calls, that is, functions provided by the kernel. 3 Subroutines, that is, library functions. 4 Devices, that is, special files in the /dev directory. 5 File format descriptions, e.g. /etc/passwd. 6 Games, self-explanatory. 7 Miscellaneous, e.g. macro packages, conventions. 8 System administration tools that only root can execute. 9 Another (Linux specific) place for kernel routine documentation. n (Deprecated) New documentation, that may be moved to a more appropriate section. o (Deprecated) Old documentation, that may be kept for a grace period. l (Deprecated) Local documentation referring to this particular system.
The name of the man page's source file (the input to the formatting system) is the name of the command, function or file name, followed by a dot, followed by the section character. If you write the documentation on the format of the `passwd' file you have to name the source file `passwd.5'. Here we also have an example of a file name that is the same as a command name. There might be even a library subroutine named passwd. Sectioning is the usual way to resolve these ambiguities: The command description is found in the file `passwd.1' and the hypothetical library subroutine in `passwd.3'.
Please do not use the n, o and l sections; according to the File System Standard these sections are deprecated. Stick to the numeric sections. Beware of name clashes with existing programs, functions or file names. It is certainly a bad idea to write yet another editor and call it ed, sed (for smart ed) or red (for Rocky's ed). By making sure your program's name is unique, you avoid having someone execute your program but read someone else's man page, or vice versa.
Now we know the name to give our file. The next decision is the directory
in which it will finally be installed (say, when the user runs `make install' for
your package.) On Linux, all man pages are below directories listed
in the environment variable MANPATH. The doc-related tools use MANPATH
in the same way the shell uses PATH to locate executables. In fact, MANPATH
has the same format as PATH. Each contains a colon-separated list of directories
(with the exception that MANPATH does not allow empty fields and relative
pathnames -- it uses absolute names only.) If MANPATH is not set or not exported,
a default will be used that contains at least the /usr/man directory. To
speed up the search and to keep directories small, the directories specified
by MANPATH (the so-called base directories) contain a bunch of subdirectories
named `man<s>' where <s> stands for the one-character section designator
introduced in the table above. Not all of the sections may be represented
by a subdirectory because there simply is no reason to keep an empty `mano'
subdirectory. However, there may be directories named `cat<s>', `dvi<s>'
and `ps<s>' which hold documentation that is ready to display or
print. More on this later. The only other file in any base directory should
be a file named `whatis'. The purpose and creation of this file will also
be described under paragraph 12). The safest way to have a man page for
section <s> installed in the right place is to put it in the directory
/usr/man/man<s>. A good Makefile, however, will allow the user to
chose a base directory, by means of a make variable, MANDIR, say. Most
of the GNU packages can be configured with the --prefix=/what/ever option.
The manuals will then be installed under the base directory /what/ever/man.
I suggest you also provide a way to do something similar.
With the advent of the Linux File System Standard (FS-Stnd), things became more complicated. The FS-Stnd 1.2 states that
This is achieved by introducing another directory level that distinguishes between different languages. Quoting again from FS-Stnd 1.2:
(See the FS-Stnd for a few common <locale> strings.) According to these guidelines, we have our man pages in /usr/man/<locale>/man[1-9lno]. The formatted versions should then be in /usr/man/<locale>/cat[1-9lno] of course, otherwise we could only provide them for a single locale. HOWEVER, I can not recommend switching to that structure at this time. The FS-Stnd 1.2 also allows that
man[1-9] directories)
directly in /usr/man. (That is the traditional circumstance and arrangement
in fact.)"I would not switch until all tools (like xman, tkman, info and many others that read man pages) can cope with the new structure.
3) How should a formatted man page
look?
Let me present you an example. Below I will explain it in detail. If
you read this as plain text it will not show the different typefaces (bold
and italics). Please refer to the paragraph "What
are the font conventions?" for further explanations. Here comes
the man page for the (hypothetical) foo program.
FOO(1) User Manuals FOO(1)
NAME
foo - frobnicate the bar library
SYNOPSIS
foo [-bar] [-c config-file ] file ...
DESCRIPTION
foo frobnicates the bar library by tweaking internal symbol
tables. By default it parses all baz segments and rearranges
them in reverse order by time for the xyzzy(1) linker to
find them. The symdef entry is then compressed using the WBG
(Whiz-Bang-Gizmo) algorithm. All files are processed in the
order specified.
OPTIONS
-b Do not write `busy' to stdout while processing.
-c config-file
Use the alternate system wide config-file instead of
/etc/foo.conf. This overrides any FOOCONF environment
variable.
-a In addition to the baz segments, also parse the blurfl
headers.
-r Recursive mode. Operates as fast as lightning at the
expense of a megabyte of virtual memory.
FILES
/etc/foo.conf
The system wide configuration file. See foo(5) for fur-
ther details.
~/.foorc
Per user configuration file. See foo(5) for further
details.
ENVIRONMENT
FOOCONF
If non-null the full pathname for an alternate system
wide foo.conf. Overridden by the -c option.
DIAGNOSTICS
The following diagnostics may be issued on stderr:
Bad magic number.
The input file does not look like an archive file.
Old style baz segments.
foo can only handle new style baz segments. COBOL
object libraries are not supported in this version.
BUGS
The command name should have been chosen more carefully to
reflect its purpose.
AUTHOR
Jens Schweikhardt <howto at schweikhardt dot net>
SEE ALSO
bar(1), foo(5), xyzzy(1)
Linux Last change: MARCH 1995 2
Here is the explanation as I promised.
The NAME section
...is the only required section. Man pages without a name section are
as useful as refrigerators at the north pole. This section also has a
standardized format consisting of a comma-separated list of program or
function names, followed by a dash, followed by a short (usually one
line) description of the functionality the program (or function, or
file) is supposed to provide. By means of makewhatis(8),
the name sections make it into the whatis database files.
Makewhatis is the reason the name section must exist, and
why it must adhere to the format I described. In the groff
source it must look like
.SH NAME foo \- frobnicate the bar library
The \- is of importance here. The backslash is needed to make the dash distinct from a hyphenation dash that may appear in either the command name or the one line description.
The SYNOPSIS section
...is intended to give a short overview on available program options. For functions this sections lists corresponding include files and the prototype so the programmer knows the type and number of arguments as well as the return type.
The DESCRIPTION section
...eloquently explains why your sequence of 0s and 1s is worth anything at all. Here is where you write down all your knowledge. This is the Hall Of Fame. Win other programmers' and users' admiration by making this section the source of reliable and detailed information. Explain what the arguments are for, the file format, what algorithms do the dirty jobs.
The OPTIONS section
...gives a description of how each option affects program behaviour. You knew that, did you not?
The FILES section
...lists files the program or function uses. For example, it lists
configuration files, startup files, and files the program directly
operates on. It is a good idea to give the full pathname of these files
and to make the install process modify the directory part to match user
preferences: the groff manuals have a default prefix of
/usr/local, so they reference /usr/local/lib/groff/* by default.
However, if you install using 'make prefix=/opt/gnu' the references in
the man page change to /opt/gnu/lib/groff/*
The ENVIRONMENT section
...lists all environment variables that affect your program or function and tells how, of course. Most commonly the variables will hold pathnames, filenames or default options.
The DIAGNOSTICS section
...should give an overview of the most common error messages from
your program and how to cope with them. There is no need to explain
system error error messages (from perror(3)) or fatal
signals (from psignal(3)) as they can appear during
execution of any program.
The BUGS section
...should ideally be non-existent. If you are brave, you can describe here the limitations, known inconveniences and features that others may regard as misfeatures. If you are not so brave, rename it the TO DO section ;-)
The AUTHOR section
...is nice to have in case there are gross errors in the documentation or program behaviour (Bzzt!) and you want to mail a bug report.
The SEE ALSO section
...is a list of related man pages in alphabetical order. Conventionally, it is the last section. You are free to invent other sections if they really do not fit in one of those described so far. So how exactly did you generate that man page? I expected that question, here is the source, Luke:
.\" Process this file with .\" groff -man -Tascii foo.1 .\" .TH FOO 1 "MARCH 1995" Linux "User Manuals" .SH NAME foo \- frobnicate the bar library .SH SYNOPSIS .B foo [-bar] [-c .I config-file .B ] .I file .B ... .SH DESCRIPTION .B foo frobnicates the bar library by tweaking internal symbol tables. By default it parses all baz segments and rearranges them in reverse order by time for the .BR xyzzy (1) linker to find them. The symdef entry is then compressed using the WBG (Whiz-Bang-Gizmo) algorithm. All files are processed in the order specified. .SH OPTIONS .IP -b Do not write `busy' to stdout while processing. .IP "-c config-file" Use the alternate system wide .I config-file instead of .IR /etc/foo.conf . This overrides any .B FOOCONF environment variable. .IP -a In addition to the baz segments, also parse the blurfl headers. .IP -r Recursive mode. Operates as fast as lightning at the expense of a megabyte of virtual memory. .SH FILES .I /etc/foo.conf .RS The system wide configuration file. See .BR foo (5) for further details. .RE .I ~/.foorc .RS Per user configuration file. See .BR foo (5) for further details. .SH ENVIRONMENT .IP FOOCONF If non-null the full pathname for an alternate system wide .IR foo.conf . Overridden by the .B -c option. .SH DIAGNOSTICS The following diagnostics may be issued on stderr: Bad magic number. .RS The input file does not look like an archive file. .RE Old style baz segments. .RS .B foo can only handle new style baz segments. COBOL object libraries are not supported in this version. .SH BUGS The command name should have been chosen more carefully to reflect its purpose. .SH AUTHOR Jens Schweikhardt <howto at schweikhardt dot net> .SH "SEE ALSO" .BR bar (1), .BR foo (5), .BR xyzzy (1)
4) How do I document several programs/functions
in a single man page?
Many programs (grep, egrep) and functions
(printf, fprintf, ...) are documented in a
single man page. However, these man pages would be quite useless if they
were only accessible under one name. We cannot expect a user to remember
that the egrep man page is actually the grep
man page. It is therefore necessary to have the man page available under
different names. You have several possibilities to achieve this:
groff's `source' mechanism provided by the
.so macro.The first way is obviously a waste of disk space. The second is not
recommended because intelligent versions of the catman program can save
a lot of work by looking at the the file type or contents. Hard links will
prevent catman from being clever. (Note that catman's purpose is to format all man
pages so they can be displayed quickly.) The third alternative
has a slight drawback: if flexibility is a concern, you have to be aware
that there are file systems that do not support symbolic links. The upshot
of this is that the Best Thing (TM) is using groff's source mechanism.
Here is how to do it: If you want to have your man page available under
the names `foo' and `bar' in section 1, then put the man page in foo.1
and have bar.1 look like this:
.so man1/foo.1
It is important to specify the man1/ directory part as
well as the file name `foo.1' because when groff is run by
the browser it will have the manual base directory as its current
working directory (cwd) and groff interprets
.so arguments relative to the cwd.
5) Which macro package should I use?
There are a number of macro packages especially designed for use in
writing man pages. Usually they are in the groff macro directory /usr/lib/groff/tmac.
The file names are tmac.<something>, where <something>
is the argument to groff's -m option. Groff will use tmac.<something>
when it is given the `-m <something>' option. Often the
blank between `-m' and `<something>' is omitted so we may
say `groff -man' when we are formatting man pages using the tmac.an
macro package. That is the reason for the strange name `tmac.an'. Besides
tmac.an there is another popular macro package, tmac.doc, which
originated at the University of California at Berkeley. Many BSD man pages
use it and it seems that UCB has made it its standard for documentation.
The tmac.doc macros are much more flexible but alas, there are
manual browsers that will not use them but always call groff -man.
For example, all xman programs I have seen will screw up on man
pages requiring tmac.doc. So do yourself a favor: use tmac.an
-- use of any other macro package is considered harmful. tmac.andoc
is a pseudo macro package that takes a look at the source and then
loads either tmac.an or tmac.doc. Actually, any man page
browser should use it but to this point, not all of them do, so it is best we
cling to ye olde tmac.an. Anything I tell you from now on and
concerning macros only holds true for tmac.an. If you want to
use the tmac.doc macros anyway, here is a pointer to detailed
information on how to use them:
http://www.FreeBSD.org/cgi/man.cgi.
There is a searchable index form on the page. Enter groff_mdoc
and it will find you groff_mdoc(7), a tutorial sampler for writing
BSD man pages. Some distros (I'm told) also come with
mdoc(7), mdoc.samples(7) and groff_man(7).
troff, with all macros explained, is
the Troff User's Manual, available as
PostScript (ps, 760K) or
Portable Document Format (pdf, 240K).
by Jospeh F. Ossanna and Brian W. Kernighan, revised November 1992.
AT&T Bell Labs have made it publicly available.
Do not forget to check out the late great
W. Richard Steven's
homepage (famous for Unix Network Programming as well as
the TCP/IP Illustrated trilogy),
who also has a list of
Troff Resources
including tbl, eqn, pic and other filters.
6) What preprocessors may I use?
Groff comes with at least three preprocessors, tbl,
eqn, and pic (on some systems they are named
gtbl, geqn and gpic.) Their
purpose is to translate preprocessor macros and their data to regular
troff input. Tbl is a table preprocessor, eqn
is an equations/maths preprocessor and pic is a picture
preprocessor. Please refer to the man pages for more information on what
functionality they provide. To put it in a nutshell: do not write man
pages requiring any preprocessor. Eqn will generally produce
terrible output for typewriter-like devices, unfortunately the type of
device 99% of all man pages are viewed on (well, at least I do). For
example, XAllocColor.3x uses a few formulas with exponentiation. Due to
the nature of typewriter-like devices, the exponent will be on the same
line as the base. N to the power of two appears as `N2'.
Tbl should be avoided because all xman programs I have seen
fail on them. Xman 3.1.6 uses the following command to format man pages,
e.g. signal(7):
gtbl /usr/man/man7/signal.7 | geqn | gtbl | groff -Tascii -man /tmp/xmana01760
2> /dev/null
which screws up for sources using gtbl, because
gtbl output is fed again into gtbl. The effect
is a man page without your table. I do not know if it is a bug or a
feature that gtbl chokes on its own output or if xman could
be a little smarter and not use gtbl twice. Furthermore,
some systems use grog to determine what options to pass to
groff. Unfortunately grog sometimes guesses wrong and recommends
groff -t when in fact tbl must not be used.
We are basically left with two workarounds for tables:
tbl macros you like but distribute the
tbl output instead of the input. There is however this
quirk with grog who thinks that any file containing a line
starting with .TS requires tbl.
Tbl output for some reason unbeknownst to me still contains
.TS and .TE. It seems you can simply remove
them and have the result still look okay. YMMV, so please test this with
your particular man page.I have yet to see a man page requiring pic
preprocessing. But I would not like it. As you can see above,
xman will not use it and groff will certainly
do the funky wadakiki on the input.
7) Should I distribute source and/or
already formatted documentation?
Let me give the pros (+) and cons (-) of a few selected possibilities:
groff.groff. groff. groff.groff.IMHO it is best to distribute source only. The argument that it is
inaccessible on systems without groff does not matter. The
500+ man pages of the Linux Documentation Project are source only. The
man pages of XFree86 are source only. The man pages from the FSF are
source only. In fact, I have rarely seen software distributed with
formatted man pages. If any sysadmin is really concerned about having
man pages accessible then he also has groff installed.
8) What are the font conventions?
First of all: do not use direct font operators like \fB,
\fP etc. Use macros which take arguments. This way you
avoid a common glitch: forgetting the font change at the end of the word
and having the bold or italic extend up to the next font change. Believe
me, it happens more often than you think. The tmac.an
macros provide the following type faces:
X alternating with Y means that the odd arguments are typeset in X while the even arguments are typeset in Y. For example
The double quotes are needed to include white space into an argument; without them, no white space appears between the alternating typefaces. In fact, you will only need the macros for alternating typefaces in cases where you want to avoid white space between typeface changes. So much for what is available. Here is how you should make use of the different typefaces: (portions shamelessly stolen from man(7))
Although there are many arbitrary conventions for man pages in the UNIX world, the existence of several hundred Linux-specific man pages defines our 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:
Filenames are always in italics, except in the SYNOPSIS section, where included files are in bold. So you should use
and
Special macros, which are usually in upper case, are in bold:
When enumerating a list of error codes, the codes are in bold. This list usually uses the .TP (paragraph with hanging tag) macro as follows:
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, without any spaces:
Acronyms look best when typeset in small type face. So I recommend
Following are some guidelines that increase reliability, readability and 'formatability' of your documentation.
groff complain when you format
your man page? It is nice to have the groff command line in
a comment. Does the man(1) command complain when you call
man yourprog? Does it produce the expected result? Will
xman(1x) and tkman(1tk) cope with your manual?
XFree86 3.1 has xman 3.1.6 - X11R6, it will try to uncompress using gzip -c -d < %s > %s
zcat < %s > %s makewhatis(8) be able to extract the one-line
description from the NAME section?rman from
http://polyglotman.sourceforge.net/,
and view the result with a a set of web browsers (netscape, mozilla, opera, lynx, ...)
Check that the cross-references among your man pages work as hyperlinks in the
generated HTML. If your software package has a web site, post its man pages
there, and keep them up-to-date.rman utility can also translate man pages into LaTeX, RTF, SGML, and other
formats; check these out if you want to incorporate your man pages in a book or
other larger document.man2html, which has been part of the
Linux man package since man-1.4. The man2html utility is a less ambitious translator than
rman, but almost every Linux user has it already, so it is worth making sure that
man2html does not choke on your man page.10) How do I get a plain text man page
without all that ^H^_ stuff?
Have a look at col(1), because col can filter out backspace
sequences. Just in case you cannot wait that long:
funnyprompt$ groff -t -e -mandoc -Tascii manpage.1 | col -bx >
manpage.txt
The -t and -e switches tell
groff to preprocess using tbl and
eqn. This is overkill for man pages that do not require
preprocessing but it does no harm apart from a few CPU cycles wasted. On
the other hand, not using -t when it is actually required
does harm: the table is terribly formatted. You can even find out (well,
"guess" is a better word) what command is needed to format a
certain groff document (not just man pages) by issuing
funnyprompt$ grog /usr/man/man7/signal.7
groff -t -man /usr/man/man7/signal.7
"Grog" stands for "GROff Guess", and it does what
it says--guess. If it were perfect we would not need options any more.
I have seen it guess incorrectly on macro packages and on preprocessors.
Here is a little perl script I wrote that can delete the page headers
and footers, thereby saving you a few pages (and mother nature a tree)
when printing long and elaborate man pages. Save it in a file named
strip-headers & chmod 755.
#!/usr/bin/perl -wn
# make it slurp the whole file at once:
undef $/;
# delete first header:
s/^\n*.*\n+//;
# delete last footer:
s/\n+.*\n+$/\n/g;
# delete page breaks:
s/\n\n+[^ \t].*\n\n+(\S+).*\1\n\n+/\n/g;
# collapse two or more blank lines into a single one:
s/\n{3,}/\n\n/g;
# see what is left...
print;
You have to use it as the first filter after the man
command as it relies on the number of newlines being output by
groff. For example:
funnyprompt$ man bash | strip-headers | col -bx > bash.txt
11) How do I get a high quality PostScript
man page?
funnyprompt$ groff -t -e -mandoc -Tps manpage.1 > manpage.ps
Print or view that using your favorite PostScript printer/viewer. See question 10) for an explanation of the options.
12) How do I get `apropos' and `whatis'
to work?
Suppose you wonder what compilers are installed on your system and how these can be invoked. To answer this (frequently asked) question you say
funnyprompt$ apropos compiler
f77 (1) - Fortran 77 compiler
gcc (1) - GNU C and C++ compiler
pc (1) - Pascal compiler
Apropos and whatis are used to quickly
report which man page has information on a certain topic. Both programs
search a number of files named `whatis' that may be found in each of the
manual base directories. As previously stated, the whatis data base files
contain a one line entry for any man page in the respective directory
tree. In fact, that line is exactly the NAME section (to be precise:
joined on one line and with hyphenation removed; note that the section
is mentioned within parentheses). The whatis database files are created
with the makewhatis(8) program. There are several versions
around, so please refer to the man page to determine what options are
available. In order for makewhatis to be able to extract
the NAME sections correctly it is important that you, the manual writer,
adhere to the NAME section format described under question
3). The differences between apropos and
whatis are simply where in the line they look, and what
they are looking for. Apropos (which is equivalent to
man -k) searches the argument string anywhere on the line,
whereas whatis (equivalent to man -f) tries to
match a complete command name only on the part before the dash.
Consequently, `whatis cc' will report if there is a
cc manual and remain quiet for gcc.
Corrections and suggestions welcome!
Copyright 1995-2001 by Jens Schweikhardt. All rights reserved.
"Two clause" BSD License:
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE.
If your name is missing here, drop me a note.
weblint -pedantic.
Paragraph 6: Added workarounds for
tbl screw-ups. Added appendices B)
and C). Added RCS Id.curl http://www.schweikhardt.net/man_page_howto.html | \
sed -e 's|<P><FONT SIZE="+2"><STRONG>\(.*\)</STRONG></FONT></P>|<h1>\1</h1>|g' \
-e 's|<P><FONT SIZE="+1"><STRONG>\(.*\)</STRONG></FONT></P>|<h2>\1</h2>|g' \
-e 's|<STRONG><FONT SIZE="+1">|<h2>|g' \
-e 's|</FONT></STRONG>|</h2>|g' \
> /var/www/html/Public/Content/z/About/man_page_howto.html and then added this block.
The sed changes allow my sites cascading style sheet to deal with the headers.
My wrapper script applies the cascading
style sheet to the page and adds the menu bar.
Saturday, December 21, 2024 @ 2:42:36 AM
z.ServerAdmin@lam1.us