C2MAN(1) C2MAN(1)
March 2, 1995
NAME
c2man - generate manual pages from C source code
SYNOPSIS
c2man [ option ... ] [ file ... ]
DESCRIPTION
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:
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% 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
By default, a separate output file is generated for each global
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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
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
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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
enumerated 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
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.
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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
};
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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 */
};
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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
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
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);
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/* 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);
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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;
non-zero (but not necessarily 1) if it does.
Extra Sections
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
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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.
OPTIONS
-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.
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-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
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(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
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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:
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% 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.
FILES
/usr/local/lib/c2man/eg/*.[ch]
A few example input files, showing different commenting styles.
SEE ALSO
man(1), apropos(1), catman(8), cproto(1), cc(1), cpp(1)
DIAGNOSTICS
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.
HISTORY
c2man was originally written by:
Graham Stoney
Canon Information Systems Research Australia
greyham@research.canon.com.au
(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.
BUGS
The -F option only interprets the following character escape
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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.
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