Use getopt() & getopt_long() to Parse Arguments

Today I came across a function [getopt] by accident.
It is very useful to parse command-line arguments with this tool!

Here is:

#inlcude <unistd.h>
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);

Explain for getopt():

Arguments argc and argv are the argument count and array as passed to the main() function.

optstring is the options set. One semicolon following a character means that character need a argument, and two semicolon mean the argument is optional.

optind is the index of the next element to be processed in argv. The system initializes this value to 1. You can reset it to 1 to restart scanning of the same argv, or when scanning a new argument vector.

If there are no more option characters, getopt() returns -1 or, it will keep return the ASCII of the current character.

optarg points to the argument string of one option if that option has argument following.

E.g.

#include <unistd.h>
#include <stdio.h>
#include <stdbool.h> // bool type
/* Macro Definition */
#define NO 0
#define YES 1
#define OK 0
#define ERROR -1

/* Structure for Global Arguments */
struct GlbArgs_t{
    bool version;
    bool help;
    char *number;
    char *type;
}GlbArgs;

/* Options allowed */
static const char *optString = "n:t::vh?";
/* Usage */
static const char *usage = "Usage: \n"
                           "-n\n"
                           "-tx (x=type-name) \n"
                           "-v\n"
                           "-h -?\n";
/* Initialize Global Argument structure */
void InitGlbArg()
{
    GlbArgs.version = NO;
    GlbArgs.help    = NO;
    GlbArgs.number  = NULL;
    GlbArgs.type    = NULL;
}

int main(int argc, char **argv)
{
    int opt = 0; // option

    InitGlbArg();

    while((opt = getopt(argc, argv, optString)) != ERROR){
        switch(opt){
        case 'n':
            GlbArgs.number = optarg;
            printf("Number: %s\n", GlbArgs.number);
            break;
        case 't':
            GlbArgs.type = optarg;
            printf("Type: %s\n", GlbArgs.type);
            break;
        case 'v':
            GlbArgs.version = YES;
            printf("Version: 1.0\n");
            break;
        case 'h':
        case '?':
            printf("%s", usage);
            break;
        default:
            break;
        }
    }

    return OK;
}

Learn a lot from here
For more details, refer to [man 3 getopt] (LInux)

巴特西

Use getopt() & getopt_long() to Parse Arguments

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