.Dd $Mdocdate: March 22 2009 $
.Dt manuals 7
.Os
.\" SECTION
.Sh NAME
.Nm Writing UNIX Documentation
.Nd a guide to writing UNIX manuals
.\" SECTION
.Sh DESCRIPTION
.Em A utility without good documentation is of no utility at all .
.\" PARAGRAPH
.Pp
A system component's documentation describes the utility of that
component, whether it's a device driver, an executable or, most
importantly, a game.  Although there are plenty of documents available
on how to read 
.Ux 
documents, or where to find them, few focus on composition.
.\" PARAGRAPH
.Pp
This document serves as a tutorial to writing 
.Ux 
documentation
.Pq Dq manuals .
If you add something to your operating system, whether it's a new file
format or directory structure or device driver, it needs documentation.
.\" SECTION
.Sh COMPOSITION
Prepare your composition environment by copying over the manual template
from 
.Pa /usr/share/misc/mdoc.template .
.Em \&Do not
start afresh or by copying another manual unless you know exactly what
you're doing!
.\" SUBSECTION
.Ss Section Numbering
Find an appropriate section for your manual.  There may exist multiple
manual names per section, so be specific.  A table of all available
manual sections follows:
.Pp
.\" LIST
.Bl -tag -width "XXXXXXXXXXXX" -offset indent -compact
.It Em Section
.Em Description
.It 1
operator utilities
.It 2
system calls
.It 3, 3p, 3f
programming libraries (C, Perl, Fortran)
.It 5
file and wire protocol formats
.It 6
games
.It 7
tutorials, documents and papers
.It 8 
administrator utilities
.It 9
in-kernel routines
.El
.Pp
If your manual falls into multiple categories, choose the most
widely-used or, better, re-consider the topic of your manual to be more
specific.  You can list all manuals per section by invoking
.Xr apropos 1 ,
then provide the
.Fl s
flag to
.Xr man 1
to see the specific section manual (section 1, in this example):
.\" DISPLAY
.Bd -literal -offset indent
% apropos myname
myname (1) - some description here
% man \-s 1 myname
.Ed
.\" SUBSECTION
.Ss Naming
Name your component.  Be terse, erring on the side of clarity.  You may
want to look for other manuals by that same name before committing:
.Pp
.Dl % apropos myname
.Pp
Manual files are named 
.Pa myname.mysection ,
such as
.Pa manuals.7
for this document.
.\" SUBSECTION
.Ss Input Language
Manuals should 
.Em always 
be written in the
.Xr mdoc 7
formatting language.
.Pp
There exist other documentation-specific languages, such as the
historical
.Xr me 7 ,
.Xr ms 7
and
.Xr man 7
packages of 
.Xr roff 7 ;
newer languages such as DocBook, texinfo or schema-driven XML; or even
ad-hoc conventions such as README files.  
.Em Avoid these formats .
Historical formats fail to capture a manual's semantic content, instead
only modelling its style.  Newer methods requires special,
system-specific tools and may change or become obsolete over the
life-time of your component.
.Pp
There are two canonical references for writing mdoc.  Read them.
.Pp
.\" LIST
.Bl -tag -width XXXXXXXXXXXXXXXX -offset indent -compact
.It Xr mdoc 7
formal language reference
.It Xr mdoc.samples 7
macro reference
.El
.Pp
Open the template you've copied into
.Pa name.section
and begin editing.
.\" SUBSECTION
.Ss Development Tools
While writing, make sure that your manual is correctly structured:
.Pp
.Dl % mandoc \-Tlint \-Wall name.1
.Pp
You may spell-check your work as follows:
.Pp
.Dl % deroff name.1 | spell
.Dl % ispell \-n name.1
.Pp
Use 
.Xr cvs 1
or, if not available,
.Xr rcs 1
to version-control your work.  If you wish the last check-in to effect
your document's date, use the following RCS tag for the date macro:
.Pp
.Dl \&.Dd $Mdocdate: March 22 2009 $
.\" SUBSECTION
.Ss Viewing
mdoc documents may be paged to your terminal with traditional 
tools such as
.Xr nroff 1 ,
.Xr groff 1 ,
or with newer, more powerful tools such as
.Xr mandoc 1 :
.\" DISPLAY
.Bd -literal -offset indent
% nroff \-mandoc name.1 | less
% groff \-Tascii \-mandoc name.1 | less
% mandoc name.1 | less
.Ed
.Pp
Other output formats are also supported:
.\" DISPLAY
.Bd -literal -offset indent
% groff \-Tps \-mandoc name.1 | less
% mandoc \-Thtml name.1 | less
.Ed
.\" SUBSECTION
.Ss Automation
Consider adding your mdoc documents to 
.Xr make 1
Makefiles in order to automatically check your input and generate
output:
.Bd -literal -offset indent
\&.SUFFIXES: .html .txt .1 .in

\&.in.1:
	mandoc -Wall,error -Tlint $<
	cp -f $< $@
\&.1.html:
	mandoc -Thtml $< >$@
\&.1.txt:
	mandoc -Tascii $< | col -b >$@
.Ed
.\" SECTION
.Sh BEST PRACTICES
The
.Xr mdoc 7
and 
.Xr mdoc.samples 7
files are indispensable in guiding composition.  In this section, we
introduce some 
.Ux
manual best practices:
.\" SUBSECTION
.Ss Language
.Bl -enum 
.It
Use clear, concise language.  Favour simplicity.
.It
Write your manual in non-idiomatic English.  Don't worry about
Commonwealth or American spellings \(em just correct ones.
.It
Spell-check your manual, keeping in mind short-letter terms (
.Xr iwi 4
vs.
.Xr iwn 4 ) .
.It
If you absolutely must use special characters (diacritics, mathematical
symbols and so on), use the escapes dictated in
.Xr mdoc 7 .
.El
.\" SUBSECTION
.Ss References 
Other components may be referenced with the
.Sq \&Xr
and
.Sq \&Sx
macros.  Make sure that these exist.  If you intend to distribute your
manual, make sure
.Sq \&Xr
references are valid across systems (within reason).  If you cross-link with
.Sq \&Sx ,
make sure that the section reference exists.
.\" SUBSECTION
.Ss Citations
Cite your work.  If your system references standards documents or other
publications, please use the
.Sq \&Rs/Re
block macros.
.\" SUBSECTION
.Ss Formatting
.Em Don't style your manual.  
Give it meaningful content.  The front-end will worry about formatting
and style.
.\" SECTION
.Sh MAINTENANCE
As your component changes and bugs are fixed, your manual may become out
of date.  You may be tempted to use automation tools like Doxygen to
smooth the development of your manuals.  Don't.  Source documentation is
different from a component manual.