C getopt不会读取所有参数

Question

I have an assignment in C that requires options to be read in for different forms of a program. Before I start on that, though, I want to make sure that the getopt portion is working fine. However, the program keeps dropping the last parameter and I don't know why. Whenever I enter the last char, the program goes to the default value that kills the program. Any help is appreciated!

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

int main(int argc, char **argv)
{
    int sFlag = 0;
    int lFlag = 0;
    int dFlag = 0;
    int rFlag = 0;
    int c;
    opterr = 0;

    while ((c = getopt (argc, argv, "slr:")) != -1)
    {
        switch(c)
        {
            case 's':
                sFlag = 1;
                break;
            case 'l':
                lFlag = 1;
                break;
            case 'r':
                rFlag = 1;
                break;
            default:
                printf("unknown parameter introduced");
                exit(-1);
                break;
        }
    }

    printf("s = %i, l = %i, d = %i, r = %i", sFlag, lFlag, dFlag, rFlag);

    return 1;
}

Answer 1

The colon symbol after r in "slr:" tells getopt() to wait for a mandatory argument which follows -r .

Examples:

1. getopt(argc, argv, "slr:") can parse ./project -s -l -r r_arg (or ./project -r r_arg -s etc.)
2. getopt(argc, argv, "s:lr:") can parse ./project -s s_arg -l -r r_arg
3. getopt(argc, argv, "s:lr:") can also parse ./project -s -l -r r_arg with no error , but the program works differently from user's expectation. This is because getopt() expects -s to be followed by its argument, however it looks like, so the next argument -l is consumed and will not hit your switch(c) .