Hello James and Alex,

On 8/8/21 10:41 AM, Alejandro Colomar wrote:

Thanks. The patch is good and I applied it

@James: it would be helpful to explain in the commit
message how you verified these details.

@Alex: do not be shy of asking people to improve there commit
messages in this way :-).

See my modified commit message below.

Cheers,

Michael

    getopt.3: Further clarification of optstring
    
    Explain that `optstring` cannot contain a semi-colon (`;`)
    character.
    [mtk: verfiried with a small test program; see also posix/getopt.c
    in the glibc sources:
    
        if (temp == NULL || c == ':' || c == ';')
          {
            if (print_errors)
              fprintf (stderr, _("%s: invalid option -- '%c'\n"), argv[0], c);
            d->optopt = c;
            return '?';
          }
    ]
    
    Also explain that `optstring` can include `+` as an option
    character, possibly in addition to that character being used as
    the first character in `optstring` to denote `POSIXLY_CORRECT`
    behaviour.
    [mtk: verified with a small test program.]
    
    Test program below. Example runs:
    
    $ ./a.out -+
    opt = 43 (+); optind = 2
    Got plus
    $ ./a.out -';'
    ./a.out: invalid option -- ';'
    opt = 63 (?); optind = 2; optopt = 59 (;)
    Unrecognized option (-;)
    Usage: ./a.out [-p arg] [-x]
    
    Signed-off-by: James O. D. Hunt [off-list ref]
    Signed-off-by: Alejandro Colomar [off-list ref]
    Signed-off-by: Michael Kerrisk [off-list ref]
    
    8x---8x---8x---8x---8x---8x---8x---8x---8x---8x---8x---
    #include <ctype.h>
    #include <sys/types.h>
    #include <stdio.h>
    #include <stdlib.h>
    #include <unistd.h>
    
    #define printable(ch) (isprint((unsigned char) ch) ? ch : '#')
    
    static void             /* Print "usage" message and exit */
    usageError(char *progName, char *msg, int opt)
    {
        if (msg != NULL && opt != 0)
            fprintf(stderr, "%s (-%c)\n", msg, printable(opt));
        fprintf(stderr, "Usage: %s [-p arg] [-x]\n", progName);
        exit(EXIT_FAILURE);
    }
    
    int
    main(int argc, char *argv[])
    {
        int opt, xfnd;
        char *pstr;
    
        xfnd = 0;
        pstr = NULL;
    
        while ((opt = getopt(argc, argv, "p:x+;")) != -1) {
            printf("opt =%3d (%c); optind = %d", opt, printable(opt), optind);
            if (opt == '?' || opt == ':')
                printf("; optopt =%3d (%c)", optopt, printable(optopt));
            printf("\n");
    
            switch (opt) {
            case 'p': pstr = optarg;                break;
            case 'x': xfnd++;                       break;
            case ';': printf("Got semicolon\n");    break;
            case '+': printf("Got plus\n"); break;
            case ':': usageError(argv[0], "Missing argument", optopt);
            case '?': usageError(argv[0], "Unrecognized option", optopt);
            default:
                      printf("Unexpected case in switch()\n");
                      exit(EXIT_FAILURE);
            }
        }

        if (xfnd != 0)
            printf("-x was specified (count=%d)\n", xfnd);
        if (pstr != NULL)
            printf("-p was specified with the value \"%s\"\n", pstr);
        if (optind < argc)
            printf("First nonoption argument is \"%s\" at argv[%d]\n",
                    argv[optind], optind);
        exit(EXIT_SUCCESS);
    }

-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/