GETARG(3) | Library Functions Manual | GETARG(3) |
NAME¶
getarg, arg_printusage — collect command line optionsSYNOPSIS¶
#include <getarg.h> intgetarg(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; };
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;
- 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
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.
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); }
$ 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 integreated with SL. It's very confusing that the struct you pass in is called getargS.SEE ALSO¶
getopt(3)September 24, 1999 | ROKEN |