arg_printusage man page on OpenBSD

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GETARG(3)		  OpenBSD Programmer's Manual		     GETARG(3)

     getarg, arg_printusage - collect command line options

     #include <getarg.h>

     getarg(struct getargs *args, size_t num_args, int argc, char **argv, int

     arg_printusage(struct getargs *args, size_t num_args, const char
     *progname, const char *extra_string);

     getarg() collects any command line options given to a program in an
     easily used way.  arg_printusage() pretty-prints the available options,
     with a short help text.

     args is the option specification to use, and it's an array of struct
     getargs elements.	num_args is the size of args (in elements).  argc and
     argv are the argument count and argument vector to extract option from.
     optind is a pointer to an integer where the index to the last processed
     argument is stored, it must be initialised to the first index (minus one)
     to process (normally 0) before the first call.

     arg_printusage take the same args and num_args as getarg; progname is the
     name of the program (to be used in the help text), and extra_string is a
     string to print after the actual options to indicate more arguments. The
     usefulness of this function is realised only be people who has used
     programs that has help strings that doesn't match what the code does.

     The getargs struct has the following elements.

     struct getargs{
	 const char *long_name;
	 char short_name;
	 enum { arg_integer,
	 } type;
	 void *value;
	 const char *help;
	 const char *arg_help;

     long_name is the long name of the option, it can be NULL, if you don't
     want a long name.	short_name is the characted to use as short option, it
     can be zero. If the option has a value the value field gets filled in
     with that value interpreted as specified by the type field.  help is a
     longer help string for the option as a whole, if it's NULL the help text
     for the option is omitted (but it's still displayed in the synopsis).
     arg_help is a description of the argument, if NULL a default value will
     be used, depending on the type of the option:

     arg_integer	the argument is a signed integer, and value should
			point to an int.

     arg_string		the argument is a string, and value should point to a

     arg_flag		the argument is a flag, and value should point to a
			int.  It gets filled in with either zero or one,
			depending on how the option is given, the normal case
			being one. Note that if the option isn't given, the
			value isn't altered, so it should be initialised to
			some useful default.

     arg_negative_flag this is the same as arg_flag but it reverses the
			meaning of the flag (a given short option clears the
			flag), and the synopsis of a long option is negated.

     arg_strings	the argument can be given multiple times, and the
			values are collected in an array; value should be a
			pointer to a struct getarg_strings structure, which
			holds a length and a string pointer.

     arg_double		argument is a double precision floating point value,
			and value should point to a double.

     arg_collect	allows more fine-grained control of the option parsing
			process.  value should be a pointer to a
			getarg_collect_info structure:

			typedef int (*getarg_collect_func)(int short_opt,
							   int argc,
							   char **argv,
							   int *optind,
							   int *optarg,
							   void *data);

			typedef struct getarg_collect_info {
			    getarg_collect_func func;
			    void *data;
			} getarg_collect_info;

			With the func member set to a function to call, and
			data to some application specific data. The parameters
			to the collect function are:

			short_flag non-zero if this call is via a short option
			flag, zero otherwise

			argc, argv the whole argument list

			optind pointer to the index in argv where the flag is

			optarg pointer to the index in argv[*optind] where the
			flag name starts

			data application specific data

			You can modify *optind, and *optarg, but to do this
			correct you (more or less) have to know about the
			inner workings of getarg.

			You can skip parts of arguments by increasing *optarg
			(you could implement the -z3 set of flags from gzip
			with this), or whole argument strings by increasing
			*optind (let's say you want a flag -c x y z to specify
			a coordinate); if you also have to set *optarg to a
			sane value.

			The collect function should return one of
			ENOMEM on error, zero otherwise.

			For your convenience there is a function,
			getarg_optarg(), that returns the traditional argument
			string, and you pass it all arguments, sans data, that
			where given to the collection function.

			Don't use this more this unless you absolutely have

     Option parsing is similar to what getopt uses. Short options without
     arguments can be compressed (-xyz is the same as -x -y -z), and short
     options with arguments take these as either the rest of the argv-string
     or as the next option (-ofoo, or -o foo).

     Long option names are prefixed with -- (double dash), and the value with
     a = (equal), --foo=bar.  Long option flags can either be specified as
     they are (--help), or with an (boolean parsable) option (--help=yes,
     --help=true, or similar), or they can also be negated (--no-help is the
     same as --help=no), and if you're really confused you can do it multiple
     times (--no-no-help=false, or even --no-no-help=maybe).

     #include <stdio.h>
     #include <string.h>
     #include <getarg.h>

     char *source = "Ouagadougou";
     char *destination;
     int weight;
     int include_catalog = 1;
     int help_flag;

     struct getargs args[] = {
	 { "source",	  's', arg_string,  &source,
	   "source of shippment", "city" },
	 { "destination", 'd', arg_string,  &destination,
	   "destination of shippment", "city" },
	 { "weight",	  'w', arg_integer, &weight,
	   "weight of shippment", "tons" },
	 { "catalog",	  'c', arg_negative_flag, &include_catalog,
	   "include product catalog" },
	 { "help",	  'h', arg_flag, &help_flag }

     int num_args = sizeof(args) / sizeof(args[0]); /* number of elements in args */

     const char *progname = "ship++";

     main(int argc, char **argv)
	 int optind = 0;
	 if (getarg(args, num_args, argc, argv, &optind)) {
	     arg_printusage(args, num_args, progname, "stuff...");
	     exit (1);
	 if (help_flag) {
	     arg_printusage(args, num_args, progname, "stuff...");
	     exit (0);
	 if (destination == NULL) {
	     fprintf(stderr, "%s: must specify destination\n", progname);
	 if (strcmp(source, destination) == 0) {
	     fprintf(stderr, "%s: destination must be different from source\n");
	 /* include more stuff here ... */

     The output help output from this program looks like this:

     $ ship++ --help
     Usage: ship++ [--source=city] [-s city] [--destination=city] [-d city]
	[--weight=tons] [-w tons] [--no-catalog] [-c] [--help] [-h] stuff...
     -s city, --source=city	 source of shippment
     -d city, --destination=city destination of shippment
     -w tons, --weight=tons	 weight of shippment
     -c, --no-catalog		 include product catalog

     It should be more flexible, so it would be possible to use other more
     complicated option syntaxes, such as what ps(1), and tar(1), uses, or the
     AFS model where you can skip the flag names as long as the options come
     in the correct order.

     Options with multiple arguments should be handled better.

     Should be integreated with SL.

     It's very confusing that the struct you pass in is called getargS.


ROKEN			      September 24, 1999			 ROKEN

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