Version 7 of troff

troff reads text files (written using an instream formatting language, see nroff) and formats the text for typesetting or laser printing.

The most common modern implementation is GNU groff.

The connection to Tcl is that the Tcl man pages - the only documentation that comes with the source - uses the *roff markup formatting language.

Simple Tutorial on Writing a Tcl Manpage

Firstly, always remember to look at other manual pages to see what sort of things belong!

The Header

Tcl manual pages start with:

.so man.macros
.TH name section version Tcl "Tcl Built-In Commands"
.BS
.SH NAME
names \- description
.SH SYNOPSIS
.nf
summary of commands/functions
.fi
.BE

The name is the name of the manual page.
The section is (typically) n for commands (e.g. lsearch), 3 for C API functions (e.g. Tcl_SetObjResult), or 1 for programs/shells (e.g. tclsh).
The version is the version of Tcl/extension where the page last had substantive changes.
The names is a comma-separated list of all the commands or functions documented on the page, and must (along with the description) be on a single line.
The description is a very short description of what the commands/functions do (e.g. lsearch's page says "See if a list contains a particular element"), and must be on a single line (along with the names).
The summary of commands/functions is what it says; check some examples for how to write them.

Body Sections

Sections start with a:

.SH "title of section in caps"

The quotes can be omitted if the title is a single word. If you want a subsection instead, use .SS instead of .SH

The following sections are normal for a Tcl manual page (and in this order):

NAME

Part of the header matter. Contents of section must follow idiomatic pattern since this is the part that apropos searches for.

SYNOPSIS

Part of the header matter. Quick summary for those people who never read very far into a page!

ARGUMENTS

Part of the header matter (not listed above). Table of C function argument descriptions; only for pages in section 3.

DESCRIPTION

General description of the command or function. Can be in quite a bit of depth, but the first paragraph should normally give the gist properly.

EXAMPLES

Idiomatic use of the command or function.

SEE ALSO

References to other manual pages (or books or papers or webpages or ...)

KEYWORDS

Comma-separated list of words people might look for the page under.

Other sections may be added between DESCRIPTION and EXAMPLES, and many pages omit the EXAMPLES still.