Provided by: heimdal-dev_7.8.git20221117.28daf24+dfsg-1ubuntu1_amd64 
NAME
getarg, arg_printusage — collect command line options
SYNOPSIS
#include <getarg.h>
int
getarg(struct getargs *args, size_t num_args, int argc, char **argv, int *optind);
void
arg_printusage(struct getargs *args, size_t num_args, const char *progname,
const char *extra_string);
DESCRIPTION
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,
arg_string,
arg_flag,
arg_negative_flag,
arg_strings,
arg_double,
arg_collect
} 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 char*.
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 ARG_ERR_NO_MATCH,
ARG_ERR_BAD_ARG, ARG_ERR_NO_ARG, 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 to.
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).
EXAMPLE
#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++";
int
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);
exit(1);
}
if (strcmp(source, destination) == 0) {
fprintf(stderr, "%s: destination must be different from source\n");
exit(1);
}
/* include more stuff here ... */
exit(2);
}
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
BUGS
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 integrated with SL.
It's very confusing that the struct you pass in is called getargS.
SEE ALSO
getopt(3)