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The GNU C Library

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25.3.13 Parsing of Suboptions Example

The code which might appear in the mount(8) program is a perfect example of the use of getsubopt:

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

int do_all;
const char *type;
int read_size;
int write_size;
int read_only;

enum
{
  RO_OPTION = 0,
  RW_OPTION,
  READ_SIZE_OPTION,
  WRITE_SIZE_OPTION,
  THE_END
};

const char *mount_opts[] =
{
  [RO_OPTION] = "ro",
  [RW_OPTION] = "rw",
  [READ_SIZE_OPTION] = "rsize",
  [WRITE_SIZE_OPTION] = "wsize",
  [THE_END] = NULL
};

int
main (int argc, char *argv[])
{
  char *subopts, *value;
  int opt;

  while ((opt = getopt (argc, argv, "at:o:")) != -1)
    switch (opt)
      {
      case 'a':
        do_all = 1;
        break;
      case 't':
        type = optarg;
        break;
      case 'o':
        subopts = optarg;
        while (*subopts != '\0')
          switch (getsubopt (&subopts, mount_opts, &value))
            {
            case RO_OPTION:
              read_only = 1;
              break;
            case RW_OPTION:
              read_only = 0;
              break;
            case READ_SIZE_OPTION:
              if (value == NULL)
                abort ();
              read_size = atoi (value);
              break;
            case WRITE_SIZE_OPTION:
              if (value == NULL)
                abort ();
              write_size = atoi (value);
              break;
            default:
              /* Unknown suboption. */
              printf ("Unknown suboption `%s'\n", value);
              break;
            }
        break;
      default:
        abort ();
      }

  /* Do the real work. */

  return 0;
}


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