c2man - generate manual pages from C source code
c2man [ option ... ] [ file ... ]
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 file argument is given, c2man takes
its input from the standard input.
If a .h file is written as a formal interface description when preparing
an interface spec, 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.
Since c2man will accept either function definitions or prototypes, it
can be used on either .c or .h files. If the input is a header file,
any files specified by -i options are assumed to be prerequisites, and
get parsed before the input file. (Any file whose extension begins
with ``h'', matched case-insensitively, is considered a header file.)
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:
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 */
};
/*
* do some useful work for a change.
* This function will actually get some productive
* work done, if you are really lucky.
* returns the number of milliseconds in a second.
*/
int dowork(int count, /* how much work to do */
enum Place where, /* where to do the work */
long fiveoclock /* when to knock off */);
When:
% c2man example.h
is run, this produces a file named dowork.3 which can be processed by
man(1) or used as:
% nroff -man dowork.3
to produce:
dowork(3) UNIX Programmer's Manual dowork(3)
NAME
dowork - do some useful work for a change.
SYNOPSIS
#include <example.h>
int dowork
(
int count,
enum Place where,
long fiveoclock
);
PARAMETERS
int count
How much work to do.
enum Place where
Where to do the work.
Possible values for an enum Place are as follows:
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.
long fiveoclock
When to knock off.
DESCRIPTION
This function will actually get some productive work
done, if you are really lucky.
RETURNS
The number of milliseconds in a second.
Output Generation [Toc] [Back]
By default, a separate output file is generated for each global identifier
(i.e. function or variable) documented by c2man.
Much of 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 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.
Global variables are not documented, unless the -v option is used.
Identifiers declared static are ignored by default unless the file is a
header file (which is most useful with inline functions) or the -s
option is used.
Declarations with the extern keyword are ignored unless they appear in
a header file; note that this does not include function definitions.
Sections Generated Automatically [Toc] [Back]
Each manual page starts with a 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 -g option, it is found after the first
dash (-) in the first comment of the file, and the -G option specifies
it explicitly.
The SYNOPSIS section begins with an #include line if the source file is
a header. After this is an external declaration for the identifier(s)
being documented.
Information in the 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.
If the manual page is for a group of functions (ie: -g or -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).
If a parameter is an enumerated type, all the possible values it can
take are output, along with their descriptions. These descriptions are
gleaned from the comments surrounding the enum identifiers where the
type was defined. Comments describing enum identifiers are placed in a
similar manner to those that describe function parameters. enum identifiers
that begin with an underscore are ignored, which is useful for
padding or _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, c2man will bunch them together to save space.
The DESCRIPTION section contains everything after the first line or
sentence of the comment describing the identifier, up until the word
``returns'' at the start of a line, matched case-insensitively and
optionally followed by a colon (:). In the case of a variable of enu-
merated type, it will also list all the values it can hold.
The 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 enumerated type, its possible
values will be listed here.
The RETURNS section is also added if there is a comment after the function
return type.
For example:
/* Sample function */
char * /* NULL if failed string otherwise */
sample_function()
{
}
The 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.
Finally, a SEE ALSO section is generated, referencing all the other
manual pages generated, if any.
The RETURNS, PARAMETERS and SEE ALSO sections are omitted entirely if
they aren't needed.
Comment Style and Placement [Toc] [Back]
Both C and C++ style comments are recognized, with seperate consecutive
single-line comments coalesced into a single block. When looking at
comments, 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.
Comments can be placed with considerable flexibility so that most commenting
styles are supported.
The following variations of the enum definition in the dowork.h 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 */
};
/* 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 */
};
/* 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
};
But the following example is 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.
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 */
};
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.
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 */
};
That may all sound a bit complex, but the upshot is that c2man will
usually know which identifier a comment is associated with, unless you
do something truly bizarre.
Processing of Comment Contents [Toc] [Back]
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 (-), an asterisk (*), or a numbered point ((n), n)
or n.), will cause a line break, allowing simple bulleted or numbered
lists.
Typesetter specific commands may be included for more complex processing,
although this isn't recommended since it ties you to a particular
typesetter.
Grouped Manual Pages [Toc] [Back]
Simple, closely related objects can be grouped together onto a single
page with the -g or -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:
/* ctype.h - character classification functions */
/* character is alphanumeric
* returns 0 if the character doesn't fit the
* classification; non-zero (but not necessarily 1)
* if it does.
*/
inline int isalnum(int c /* the character to classify */);
/* character is a letter */
inline int isalpha(int c);
/* character is a control character */
inline int iscntrl(int c);
/* character is a digit */
inline int isdigit(int c);
/* character is a graphic */
inline int isgraph(int c);
/* character is a lower case letter */
inline int islower(int c);
/* character is printable */
inline int isprint(int c);
/* character is punctuation */
inline int ispunct(int c);
/* character is a a form of whitespace */
inline int isspace(int c);
/* character is an upper case letter */
inline int isupper(int c);
/* character is a hexadecimal digit */
inline int isxdigit(int c);
then using:
% c2man -g ctype.h
yields:
ctype(3) UNIX Programmer's Manual ctype(3)
NAME
isalnum, isalpha, iscntrl, isdigit, isgraph, islower,
isprint, ispunct, isspace, isupper, isxdigit - character
classification functions
SYNOPSIS
#include <ctype.h>
inline int isalnum(int c);
inline int isalpha(int c);
inline int iscntrl(int c);
inline int isdigit(int c);
inline int isgraph(int c);
inline int islower(int c);
inline int isprint(int c);
inline int ispunct(int c);
inline int isspace(int c);
inline int isupper(int c);
inline int isxdigit(int c);
PARAMETERS
int c The character to classify.
DESCRIPTION
isalnum
Character is alphanumeric.
isalpha
Character is a letter.
iscntrl
Character is a control character.
isdigit
Character is a digit.
isgraph
Character is a graphic.
islower
Character is a lower case letter.
isprint
Character is printable.
ispunct
Character is punctuation.
isspace
Character is a a form of whitespace.
isupper
Character is an upper case letter.
isxdigit
Character is a hexadecimal digit.
RETURNS
isalnum
0 if the character doesn't fit the classification; nonzero
(but not necessarily 1) if it does.
Extra Sections [Toc] [Back]
Additional sections not otherwise recognized by 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 (:), or is a line ending with a
colon, so section names with spaces are allowed, like "Return value:".
Section heading names are capitalized, and the names DESCRIPTION,
RETURNS and NAME are recognized specially so you can name them explicitly
if you like. FUNCTION, PROCEDURE and ROUTINE are also recognised,
and treated identically to NAME.
For example:
/*
* Have a quick puff.
*
* Warning: Smoking causes lung cancer
*/
void go_for_a_smoke();
Generates a manual page with a WARNING section.
-odir Write generated files into directory dir rather than the current
directory. If dir is specified as -, generated pages are written
to the standard output, separated by form-feeds.
-v Also output declarations for variables defined in the file.
-s Output manual pages for all static identifiers.
-g Group all the info generated together into a single page (ala
ctype(3)), reading the single-line terse description for the
NAME section from the line of the first comment in the file. If
this first line contains a dash (-) 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 -l option.
-Gterse
Like -g, but using the specified terse description rather than
reading it from the file.
-k Don't attempt to fix up capitalization and punctuation.
-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.
-B Apply -b strictly. Only look for the description of a function
at the top of its body.
-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 (h) is the default, as it uses the least space. Soft link
(s), where supported, allows a find(1) command with ``-type f''
to easily skip the duplicated pages. Separate file (f) containing
a file include directive is the traditional UNIX method. No
link (n) is useful for generating printed documentation without
duplicated pages; only a single file, named according to the -n
option, is generated. Remove (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.
In all cases, any existing links will be removed before being
rewritten.
-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.
-ifile
-i"file"
-i<file>
Insert a #include line referencing the specified file in the
SYNOPSIS section, using the ``<file>'' form by default. Any
number of -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.
-xsectionname
Exclude sectionname from the generated manpages. This option
may be repeated to exclude a number of sections.
-Hheader-path
Prepend header-path to the name of the header file when an
#include line is automatically generated in the SYNOPSIS section.
-L Lazy option: Only list parameters in the 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.
-Tn|l|t|h|a[,options]
Set the output typesetting language as well as language specific
options. options is a comma delimited list of options. Nroff
(n) is the default, LaTeX (l) , Texinfo (t) , HTML (h) , or
AutoDoc (a). Texinfo specific options are s, t, n, and C.
In 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 t is given,
the name of the manpage is used for the title of the NAME section,
and is encoded as a ``section'', placing it in the table
of contents. Subsequent sections are encoded as ``headings''.
Texinfo supports multiple levels of headings; the desired level
may be specified via the sn option, where 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 c2man -e
option). If the n option is specified, a node is created in
embedded mode, but without Up, Previous, or Next pointers;
these must be filled in (Texinfo mode in emacs does a good job
of it). The C option capitalizes the section titles. Usually
they are printed as specified (which is usually upper case).
-e Prepares the output so it can be embedded in texts of the output
typesetting language.
-Mname Set the name of the manual in which the page will go.
-Ssection
Set the default manual section, used as the extension on the
output files. section defaults to ``3'' for nroff, ``texi'' for
Texinfo , ``html'' for HTML and ``tex'' for LaTeX output, as
specified via the -T option. This setting can be overridden by
the -O?.ext options for finer control.
-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 (f), variables
(v), static functions (F) and static variables (V).
If subdir is specified, the selected class of output will be
written in that subdirectory under the directory given by the -o
option if specified, otherwise under the current directory.
If .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 -S option (if specified), or the typesetting output format
specified by the -T option.
For example, the following command will generate 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):
% c2man -o/usr/local/man -v -s -Ofman3.3 -Ovman3.3v
-OFman9.9 -OVman9.9v input.c
The -O options will have no effect if -o- is used to write to
standard output, and -Ov, -OF and -OV will have no effect unless
their classes of output are enabled via the appropriate -v and
-s options.
-Ftemplate
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
" int f ( a, b )"
but you may replace each space in this string with any number of
whitespace characters. For example, the option
-F"int f(\n\ta,\n\tb\n\t)"
will produce:
int main(
int argc,
char *argv[]
)
The default output format is:
int main
(
int argc,
char *argv[]
);
-Ppreprocessor
Run a different C preprocessor than normal (use -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 gcc's cpp
instead:
% c2man -P "gcc -E -C"
-Dname[=value]
This option is passed through to the preprocessor and is used to
define symbols for use with conditionals such as #ifdef.
-Uname This option is passed through to the preprocessor and is used to
remove any definitions of this symbol.
-Idirectory
This option is passed through to the preprocessor and is used to
specify a directory to search for files that are referenced with
#include.
-V Print version information and cpp parameters.
/usr/share/doc/c2man/eg/*.[ch]
A few example input files, showing different commenting styles.
man(1), apropos(1), catman(8), cproto(1), cc(1), cpp(1)
c2man's error messages are not very helpful, so make sure your code
compiles before trying c2man. If the code compiles OK but c2man
rejects it, it may be because a comment is in a position c2man does not
accept, or you are using a compiler extension not strictly conforming
to standard C. c2man defines the preprocessor symbol __C2MAN__ with
its major version number to allow you to work around such problems by
surrounding them with #ifndef __C2MAN__.
An error at the very end of a function may indicate that the comments
at the beginning are badly placed.
c2man was originally written by:
Graham Stoney
Canon Information Systems Research Australia
[email protected]
(please send bug reports here)
Many thanks are due to the many other Internet contributors since then,
and to Chin Huang, the author of cproto from which it was originally
derived.
The -F option only interprets the following character escape sequences:
\n newline
\t tab
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.
Comments aren't legal in some of the more obscure places that they are
in C.
Heavy use of #define in a program may yield somewhat obscure manual
pages.
c2man's output backends may not be entirely consistent, but then users
of different formatters tend to have different tastes.
March 2, 1995 C2MAN(1)
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