c2man.man

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.TH C2MAN 1 "March 4, 2024"
.BY "CISRA"
.SH NAME
c2man \- generate manual pages from C source code
.SH SYNOPSIS
.B c2man
[ 
.I option \fP...\fI
] [
.I file \fP...\fI
]
.SH DESCRIPTION
.B c2man
reads C source code files in which comments have been strategically placed,
and outputs manual page(s) documenting each function defined or declared (via
a prototype), and optionally each variable with global scope.
Function definitions and declarations may be in the old style or ISO/ANSI style.
If no
.I file
argument is given,
.B c2man
takes its input from the standard input.
.PP
If a
.B .h
file is written as a formal interface description when preparing an
interface spec,
.B c2man
can generate all the manual pages required for the spec at one fell swoop,
and then keep them up to date automatically as the interface changes.
.PP
Since
.B c2man
will accept either function definitions or prototypes, it can be used on
either
.B .c
or
.B .h
files.
If the input is a
.B header
file, any files specified by
.B \-i
options are
assumed to be prerequisites, and get parsed before the input file.
(Any file whose extension begins with
.RB `` h '',
matched case-insensitively,
is considered a
.B header
file.)
.PP
This is potentially a huge win for most programmers that just love documenting
their functions, and updating the documentation every time it changes.
Here's an example, named example.h:
.IF
.so example.h
.IE
.PP
When:
.CD c2man example.h
is run,
this produces a file named
.B dowork.3
which can be processed by man(1) or used as:
.CD "nroff -man dowork.3"
to produce:
.OF
.ne 34
.so example.inc
.OE
.SS "Output Generation"
By default, a separate output file is generated for each global identifier
(i.e. function or variable) documented by c2man.
.PP
Much of
.BR c2man 's
information is extracted from the comment placed immediately before the
declaration/definition of the identifier being documented; this comment
is taken to describe the identifier and
.B must
be present, or the identifier will be ignored entirely.
In the case of a variable declaration/definition, this comment may instead be
placed after it starting on the same line.
.PP
Global variables are not documented, unless the
.B \-v
option is used.
.PP
Identifiers declared
.B static
are ignored by default unless the file is a
.B header
file (which is most useful with
.B inline
functions) or the
.B -s
option is used.
.PP
Declarations with the
.B extern
keyword are ignored unless they appear in a
.B header
file; note that this does not include function definitions.
.SS "Sections Generated Automatically"
Each manual page starts with a
.B NAME
section, listing the name(s) of the identifier(s) documented, along with a
terse description.
By default, this description is the first line or sentence of the
comment describing the identifier.
With the
.B \-g
option, it is found after the first dash
.RB ( \- )
in the first comment of the file, and the
.B \-G
option specifies it explicitly.
.PP
The
.B SYNOPSIS
section
begins with an
.B #include
line
if the source file is a
.BR header .
After this is an external declaration for the
identifier(s) being documented.
.PP
Information in the
.B PARAMETERS
section is gleaned from the comments immediately before or after each
parameter declaration. A comment after a parameter can follow the comma that
separates that parameter from the next, if the comment starts on the same line
and is the only remaining thing on that line. Leading underscores in a
parameter name are stripped when printed in the manual page.
.PP
If the manual page is for a group of functions (ie:
.B \-g
or
.B \-G
options),
identical parameters (in both name and type) common to more than one function
are described only once if only one has a comment (as in the ctype Xexample below).
.PP
If a parameter is an
.B enumerated
.BR type ,
all the possible values it can take are output, along with their descriptions.
These descriptions are gleaned from the comments surrounding the
.B enum
identifiers where the type was defined.
Comments describing
.B enum
identifiers are placed in a similar manner to those that describe function
parameters.
.B enum
identifiers that begin with an underscore are ignored, which is useful for
padding or
.I _NUMBER_OF_...
values which aren't normally used by someone calling
the function.
If none of the identifiers in an enumerated type has a comment,
.B c2man
will bunch them together to save space.
.PP
The
.B DESCRIPTION
section contains everything
after the first line or sentence
of the comment describing the identifier,
up until the word
.RB `` returns ''
at the start of a line, matched case-insensitively and optionally followed by
a colon
.RB ( : ).
In the case of a variable of
.B enumerated
.BR type ,
it will also list all the values it can hold.
.PP
The
.B RETURNS
section contains anything after that. Any of these lines that begin with a
single word followed by a colon or a tab generate tagged paragraphs so that
lists of possible return values and error codes look neat.
If the function is void, don't put anything like "Returns: nothing" in
the comment, since it's a waste of space. If the identifier is a function
returning an
.B enumerated
.BR type ,
its possible values will be listed here.
.PP
The
.B RETURNS
section is also added if there is a comment after the function return type.
.EX 5 "For example:"
/* Sample function */
char *			/* NULL if failed string otherwise */
sample_function()
{
}
.EE
The
.B RETURNS
section will contain the full contents of the comment (stripping the optional
leading asterisk). It is not possible to use both methods to specify a
description for the return value. In that case the comment after the
return type supersedes whatever was specified for the return value in
the comment above the function.
.PP
Finally, a
.B "SEE ALSO"
section is generated, referencing all the other manual pages generated, if any.
.PP
The
.BR RETURNS ,
.B PARAMETERS
and
.B "SEE ALSO"
sections are omitted entirely if they aren't needed.
.SS "Comment Style and Placement"
Both
.B C
and
.B C++
style comments are recognized,
with seperate consecutive single-line comments coalesced into a single block.
When looking at comments,
.B c2man
ignores everything before the first alpha-numeric character. After that, it
ignores leading white-space, leading asterisks and leading slashes
on all subsequent
lines, and ignores all trailing lines thus rendered blank. If that leaves
nothing, the comment is ignored entirely.
This makes it very flexible in supporting popular comment boxing.
.PP
Comments can be placed with considerable flexibility so that most commenting
styles are supported.
.EX 13 "The following variations of the enum definition in the \fBdowork.h\fR\
 example are all equivalent:"
/* commas after the comments. */
enum Place
{
    HOME       /* Home, Sweet Home */,
    WORK       /* where I spend lots of time */,
    MOVIES     /* Saturday nights mainly */,
    CITY       /* New York, New York */,
    COUNTRY    /* Bob's Country Bunker */
};
.EE
.EX 16
/* the comment needn't go on the same line,
 * if the comma goes after the comment.
 */
enum Place
{
    HOME
    	/* Home, Sweet Home */,
    WORK
    	/* where I spend lots of time */,
    MOVIES
    	/* Saturday nights mainly */,
    CITY
    	/* New York, New York */,
    COUNTRY
    	/* Bob's Country Bunker */
};
.EE
.EX 14
/* the comment can go before it too. */
enum Place
{
    /* Home, Sweet Home */
    HOME,
    /* where I spend lots of time */
    WORK,
    /* Saturday nights mainly */
    MOVIES,
    /* New York, New York */
    CITY,
    /* Bob's Country Bunker */
    COUNTRY
};
.EE
But the following example is
.B NOT
equivalent because the commas are between the identifier and the its
associated comment, and the comment is on a different line.
Each comment actually applies to the wrong identifier, so this will result in
very misleading output.
.EX 16 "Don't do this:"
enum Place
{
    HOME,
    	/* Home, Sweet Home */
    WORK,
    	/* where I spend lots of time */
    MOVIES,
    	/* Saturday nights mainly */
    CITY,
    	/* New York, New York */
    COUNTRY
    	/* Bob's Country Bunker */
};
.EE
.PP
Since enum identifiers sometimes fall into logical groups, a comment before
such an identifier will be taken to apply to the next few in the list,
provided that the comments describing each individual identifier
are placed after them. Also, there must be a blank line separating the comment
describing the next logical group and the comment at the end of the previous
line, or the two will be coalesced and incorrectly treated as a single comment
for the previous enumerator.
.EX 17 "In other words, you can go:"
/* include logical grouping comments. */
enum Place
{
    /* These take up most of the week */
    HOME,      /* Home, Sweet Home */
    WORK,      /* where I spend lots of time */

    /* More for special occasions */
    MOVIES,     /* Saturday nights mainly */
    CITY,      /* New York, New York */

    /* The real favourite */
    COUNTRY    /* Bob's Country Bunker */
};
.EE
.PP
That may all sound a bit complex, but the upshot is that
.B c2man
will usually know which identifier a comment is associated with, unless you do
something truly bizarre.
.SS "Processing of Comment Contents"
Basic punctuation and capitalisation corrections are made in each section for
neatness, and the typesetting program used to process the output will generally
reformat line breaks according to the width of the output device. Blank lines
in a comment will be preserved, and lines starting with a dash
.RB ( \- ),
an asterisk
.RB ( * ),
or a numbered point 
.RB ( (n) ,
.B n)
.RB or\  n. ), 
will cause a line break, allowing simple bulleted or numbered lists.
.PP
Typesetter specific commands may be included for more complex processing,
although this isn't recommended since it ties you to a particular typesetter.
.SS "Grouped Manual Pages"
Simple, closely related objects can be grouped together onto a single page with the
.B \-g
or
.B \-G
options. By default, this results in a single output file with multiple links
so that it can be accessed by the name of the input file, or of any identifier
documented.
For example, if ctype.h contains:
.IF
.so ctype_ex.h
.IE
.PP
then using:
.CD c2man -g ctype.h
yields:
.OF
.so ctype_ex.inc
.OE
.SS "Extra Sections"
Additional sections not otherwise recognized by
.B c2man
can be included in the manual page by including them in the comment
describing the identifier.
A section heading is preceded in the comment by an empty line (after
removal of leading asterisks), and is the only word on it's line, or is
a word followed by a colon
.RB ( : ),
or is a line ending with a colon, so section names with spaces are allowed,
like "Return value:".
.P
Section heading names are capitalized, and the names
.BR DESCRIPTION ,
.B RETURNS
and
.B NAME
are recognized specially so you can name them explicitly if you like.
.BR FUNCTION ,
.B PROCEDURE
and
.B ROUTINE
are also recognised, and treated identically to
.BR NAME .
.EX 9 "For example:"
/*
 * Have a quick puff.
 * 
 * Warning: Smoking causes lung cancer
 */
void go_for_a_smoke();
.EE
Generates a manual page with a
.B WARNING
section.
.EE
.SH OPTIONS
.TP
.BI \-o dir
Write generated files into directory
.B dir
rather than the current directory.
If
.B dir
is specified as
.BR \- ,
generated pages are written to the standard output, separated by form-feeds.
.TP
.B \-v
Also output declarations for variables defined in the file.
.TP
.B \-s
Output manual pages for all
.B static
identifiers.
.TP
.B \-g
Group all the info generated together into a single
page (ala ctype(3)), reading the single-line terse description for the
.B NAME
section from the line of the first comment in the file.
If this first line contains a dash
.RB ( \- )
surrounded by whitespace, the terse description is taken starting after the
dash.
If multiple files are specified,
the first such suitable comment encountered is used. A link to
the output file is made for each identifier documented, according to the
.B \-l
option.
.TP
.BI \-G terse
Like
.BR \-g ,
but using the specified terse description rather than reading it from the
file.
.TP
.B \-k
Don't attempt to fix up capitalization and punctuation.
.TP
.B \-b
If a function lacks a preceding comment, look for one immediately following
the curly-brace at the top of the function body.  
The comment must appear before anything else.
.TP
.B \-B
Apply 
.B \-b 
strictly.  Only look for the description of a function at
the top of its body.
.TP
.B \-l h|s|f|n|r
Select how the output for a grouped manual page is linked to files named after
all identifiers documented on the page.
Hard link
.RB ( h )
is the default, as it uses the least space.
Soft link
.RB ( s ),
where supported, allows a
.BR find (1)
command with
.RB `` "\-type f" ''
to easily skip the duplicated pages.
Separate file
.RB ( f )
containing a file include
directive is the traditional
.SM UNIX
method.
No link
.RB ( n )
is useful for generating printed documentation without duplicated pages; only
a single file, named according to the
.B \-n
option, is generated.
Remove
.RB ( r )
is like No link, but also removes any previously generated links/files named
after the identifiers documented. Useful for cleaning up after accidents with
the other link options.
.sp
In all cases, any existing links will be removed before being rewritten.
.TP
.B \-n
Name the documentation output file after the input file.
When generating grouped manual pages, this will be the file to which others
are linked. 
For non-grouped manual pages, if documentation for more than one
identifier is generated, information about the last identifier will overwrite
information about all the previous ones.
.PP
.BI \-i file
.PP
\fB\-i\fI\{"file"\}
.TP
.BI \-i <file>
Insert a
.B #include
line referencing the specified file in the
.B SYNOPSIS
section, using the ``<file>'' form by default.
Any number of
.B \-i
options may be specified to build up a list of prerequisites.
If using the second form, you may need to quote the quotation marks, lest they
get removed by the shell.
.TP
.BI \-x sectionname
Exclude
.I sectionname
from the generated manpages.  This option may be repeated to exclude a number
of sections.
.TP
.BI \-H header-path
Prepend
.B header-path
to the name of the
.B header
file when an
.B #include
line is automatically generated in the
.B SYNOPSIS
section.
.TP
.BI \-L
Lazy option: Only list parameters in the
.B PARAMETERS
section if they are documented by a comment in the source. By default,
parameters with no comment are described as ``Not Documented.'', to encourage
the programmer to comment them.
.TP
.BI \-Tn|l|t|h|a[, options ]
Set the output typesetting language as well as language specific
options.
.I options
is a comma delimited list of options.
.B Nroff
.RB ( n )
is the default, 
.B LaTeX
.RB ( l )
,
.B Texinfo
.RB ( t )
,
.B HTML
.RB ( h )
, or
.B AutoDoc
.RB ( a ).
.B Texinfo
specific options are 
.BR s ,
.BR t ,
.BR n ,
and
.BR C .

In 
.B Texinfo
mode, each section is normally coded as a ``heading'' rather than a
``section''.  This prevents the section name from appearing in the
table of contents.  If the option
.B t
is given, the name of the manpage is used for the title of the
.B NAME
section, and is encoded as a ``section'', placing it in
the table of contents.  Subsequent sections are encoded as ``headings''.  
.B Texinfo
supports multiple levels of headings; the desired level may be
specified via the 
.BI s n
option, where
.I n
starts at 0 for the ``chapter level'' and works down.  A
top level node is created for the manpage, except when in embedded
mode
(the 
.B c2man \-e
option).  If the 
.B n
option is specified, a node is created in embedded mode, but
without Up, Previous, or Next pointers;  these must be filled in
.BR ( Texinfo
mode in 
.B emacs
does a good job of it).  The
.B C
option capitalizes the section titles.  Usually they are printed
as specified (which is usually upper case).
.TP
.BI \-e
Prepares the output so it can be embedded in texts of the output typesetting
language.
.TP
.BI \-M name
Set the name of the manual in which the page will go.
.TP
.BI \-S section
Set the default manual section, used as the extension on the output files.
.I section
defaults to ``3'' for
.BR nroff ,
``texi'' for
.B Texinfo ,
``html'' for
.B HTML
and ``tex'' for
.B LaTeX
output, as specified via the
.B \-T
option.
This setting can be overridden by the
.BI \-O? .ext
options for finer control.
.TP
.BI \-Of|v|F|V[ subdir ][. ext ]
Provides for finer control of the output files, allowing a different output
subdirectory and extension to be specified for these different classes of
objects:
functions
.RB ( f ),
variables
.RB ( v ),
static functions
.RB ( F )
and static variables
.RB ( V ).
.sp
If
.I subdir
is specified, the selected class of output will be written in that
subdirectory under the directory given by the
.B \-o
option if specified, otherwise under the current directory.
.sp
If
.I .ext
is specified, it will be used as the extension on the output files of the
selected class, instead of the default based on the
.B \-S
option (if specified), or the typesetting output format specified by the
.B \-T
option.
.sp
For example, the following command will generate
.BR nroff (1)
style output under the /usr/local/man hierarchy, documenting functions in
section 3 (/usr/local/man/man3/*.3), global variables in section 3v
(/usr/local/man/man3/*.3v), static functions in section 9
(/usr/local/man/man9/*.9) and
static variables in section 9v (/usr/local/man/man9/*.9v):
.CD c2man -o/usr/local/man -v -s -Ofman3.3 -Ovman3.3v -OFman9.9 -OVman9.9v input.c
The
.B \-O
options will have no effect if
.B \-o-
is used to write to standard output, and
.BR \-Ov ,
.B \-OF
and
.B \-OV
will have no effect unless their classes of output are enabled via the
appropriate
.B \-v
and
.B \-s
options.
.TP
.BI \-F template
Set the format used to output the prototype for functions with more than 1
parameter
in each manual page;
functions with zero or 1 parameters are always output as one line.
The format is specified by a template in the form
.EX
" int f ( a, b )"
.EE
but you may replace each space in this string with any number of
whitespace characters.
For example, the option
.EX
-F"int f(\\n\\ta,\\n\\tb\\n\\t)"
.EE
.EX 5 "will produce:"
int main(
        int argc,
        char *argv[]
        )
.EE
.EX 5 "The default output format is:"
int main
(
        int argc,
        char *argv[]
);
.EE
.TP
.BI \-P preprocessor
Run a different C preprocessor than normal (use
.B \-V
to determine the configured default).
You must include any options required to prevent it from stripping comments,
which is normally the default preprocessor behaviour.
For example, to use
.BR gcc 's
cpp instead:
.CD c2man -P \{"gcc -E -C"\}
.TP
.BI \-D name[=value]
This option is passed through to the preprocessor and is used to define 
symbols for use with conditionals such as
.I #ifdef.
.TP
.BI \-U name
This option is passed through to the preprocessor and is used to remove
any definitions of this symbol.
.TP
.BI \-I directory
This option is passed through to the preprocessor and is used to specify
a directory to search for files that are referenced with 
.I #include.
.TP
.B \-V
Print version information and cpp parameters.
.SH FILES
.TP
$(privlib)/eg/*.[ch]
A few example input files, showing different commenting styles.
.SH "SEE ALSO"
man(1),
apropos(1),
catman(8),
cproto(1),
cc(1),
cpp(1)
.SH DIAGNOSTICS
.BR c2man 's
error messages are not very helpful, so make sure your code compiles before
trying
.BR c2man .
If the code compiles OK but
.B c2man
rejects it, it may be because a comment is in a position
.B c2man
does not accept, or you are using a compiler extension not strictly conforming
to standard C.
.B c2man
defines the preprocessor symbol
.B __C2MAN__
with its major version number
to allow you to work around such problems by surrounding them with
.BR "#ifndef __C2MAN__" .
.PP
An error at the very end of a function may indicate that the comments at the
beginning are badly placed.
.SH HISTORY
.B c2man
was originally written by:
.NA 4
Graham Stoney
Canon Information Systems Research Australia
greyham@research.canon.com.au
(please send bug reports here)
.NE
Its soource tree has been converted to ANSI-C and cleaned up significantly by:
.NA 4
Mark O'Neill
Tumbling Dice
mao@tumblingdice.co.uk
Newcastle uupon Tyne
UK
.NE
Many thanks are due to the many other Internet contributors since then, and to
Chin Huang, the author of
.B cproto
from which it was originally derived.
.SH BUGS
The
.B \-F
option only interprets the following
character escape sequences:
.EX 2
\\n	newline
\\t	tab
.EE
.PP
A comment before a preprocessor directive will be considered to apply
to the identifier that immediately follows, if it has no
comment of its own.
This is because the preprocessor directive gets removed by cpp before
c2man looks at it.
.PP
Comments aren't legal in some of the more obscure places that they are in C.
.PP
Heavy use of
.B #define
in a program may yield somewhat obscure manual pages.
.PP
.BR c2man 's
output backends may not be entirely consistent, but then users of
different formatters tend to have different tastes.