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.Dd December 21, 2022
.Dt AG_GETOPT 3
.Os Agar 1.7
.Sh NAME
.Nm AG_Getopt
.Nd agar incremental argument list parser
.Sh SYNOPSIS
.Bd -literal
#include <agar/core.h>
.Ed
.Sh DESCRIPTION
The
.Nm
interface parses command-line arguments.
.Sh INTERFACE
.nr nS 1
.Ft "int"
.Fn AG_Getopt "int argc" "char * const argv[]" "const char *optstring" "char **pOptArg" "int *pOptInd"
.nr nS 0
.Pp
The
.Fn AG_Getopt
function incrementally parses command-line arguments
.Fa argv
and returns the next
.Em known
option character.
A
.Em known
character is one that occurs in the dictionary specified by the
.Fa optstring
argument.
.Pp
If a character is followed by ":" in
.Fa optstring
then a string is expected to follow the option character in the command-line
arguments.
This string is returned into
.Fa pOptArg ,
if not NULL.
.Pp
The index of the last argument processed by
.Nm
is returned into
.Fa pOptInd ,
if not NULL.
.Pp
On platforms where command-line arguments are not supported,
.Fn AG_Getopt
always returns -1.
.Sh EXAMPLES
The following program uses
.Fn AG_Getopt
to parse its command-line options:
.Bd -literal -offset indent
.\" SYNTAX(c)
static int debug = 0;

int
main(int argc, char *argv[])
{
	char *optArg, *filename;
	int c, optInd, i;

	while ((c = AG_Getopt(argc, argv, "df:?h",
	                      &optArg, &optInd)) != -1) {
		switch (c) {
		case 'd':
			debug = 1;
			break;
		case 'f':
			filename = optArg;
			break;
		default:
			printf("Usage: my-program [-d] "
			       "[-f filename] [...]\\n")
			return (1);
		}
	}

	for (i = optInd; i < argc; i++)
		printf("Extra argument: %s\\n", argv[i]);

	return (0);
}
.Ed
.Sh SEE ALSO
.Xr AG_Intro 3
.Sh HISTORY
The
.Nm
interface first appeared in Agar 1.4.0.