getopt()用法

#include<stdio.h>
#include<unistd.h>

extern char *optarg;
extern int optind, optopt,opterr;

int main(int argc,char **argv)
{
        int ch;

        while((ch = getopt(argc,argv,"a:bcd")) != -1)
        switch(ch)
        {
        case 'a':
                printf("option a:'%s' ",optarg);
                break;
        case 'b':
                printf("option b :b ");
                break;
        case '?':
        case 'h':
                printf("usage ");
                break;
        default:
                printf("other option :%c ",ch);
        }
        if (1 == argc)
                printf("usage ");
        printf("optopt +%c ",optopt);
}