Getopt function usage and getopt function usage

Getopt function usage and getopt function usage

Linux provides a function to parse command line parameters.

#include <unistd.h>       int getopt(int argc, char * const argv[],                  const char *optstring);       extern char *optarg;       extern int optind, opterr, optopt;

Using this function, we can run the following command:

./a.out -n -t 100

N does not require a parameter. t requires a value as a parameter.

The Code is as follows:

#include <stdio.h>#include <stdlib.h>#include <string.h>#include <unistd.h>#include <errno.h>#define ERR_EXIT(m) \    do { \        perror(m);\        exit(EXIT_FAILURE);\    }while(0)int main(int argc, char *argv[]){    int opt;    while(1)    {        opt = getopt(argc, argv, "nt:");        if(opt == '?')            exit(EXIT_FAILURE);        if(opt == -1)            break;        switch(opt)        {            case 'n':                printf("AAAAAAAA\n");                break;            case 't':                printf("BBBBBBBB\n");                int n = atoi(optarg);                printf("n = %d\n", n);        }    }    return 0;}

If an invalid parameter is input, getopt returns '? ', When the resolution is complete,-1 is returned.

If a parameter is required, use optarg to obtain it. This is a global variable.

Note that the third parameter "nt:" Of getopt indicates that n and t are available, and t is followed by a colon, indicating that t requires additional parameters.

The running result is as follows:

5:30:22 wing@ubuntu msg ./getopt_test -nAAAAAAAA5:30:26 wing@ubuntu msg ./getopt_test -t ./getopt_test: option requires an argument -- 't'5:30:31 wing@ubuntu msg ./getopt_test -t 100                                           1 ↵BBBBBBBBn = 100