int getopt(int argc, char * const argv[], const char *optstring);
extern char *optarg; extern int optind, opterr, optopt;
#include <getopt.h>
int getopt_long(int argc, char * const argv[], const char *optstring, const struct option *longopts, int *longindex);
int getopt_long_only(int argc, char * const argv[], const char *optstring, const struct option *longopts, int *longindex); DESCRIPTION The getopt() function parses the command-line arguments. Its arguments argc and argv are the argument count and array as passed to the main() function on program invocation. An element of argv that starts with '-' (and is not exactly "-" or "--") is an option element. The characters of this element (aside from the initial '-') are option characters. If getopt() is called repeatedly, it returns successively each of the option characters from each of the option elements.
The variable optind is the index of the next element to be processed in argv. The system initializes this value to 1. The caller can reset it to 1 to restart scanning of the same argv, or when scanning a new argument vector.
If getopt() finds another option character, it returns that character, updating the external variable optind and a static variable nextchar so that the next call to getopt() can resume the scan with the follow‐ ing option character or argv-element.
If there are no more option characters, getopt() returns -1. Then optind is the index in argv of the first argv-element that is not an option.
