/* Example of using getopt to parse command line arguments.

   This code uses the getopt() function, there is a richer library
   (gnu getopt_long) as well.

   getopt supports finding command line options that begin with
   the character "-" (as in "ls -al"). Some options are simply either
   present or not, others can indicate some value. For example,
   a program that allows the user to specify two numbers to add could
   have a command line like this:

      prog -x 100 -y 200

   The progam below doesn't do anything other than print out some values
    that can be set from the command line. It supports four different
    options:
       -v : a toggle (sets the variable "verbose" to 1).
       -n num:  sets the value of a variable named d
       -x num:  sets the value of a variable named foo
          (just using x for this to make sure you realize there is
           no automatic connection between the option character and 
           what you do with the following value).
       -i filename: sets the value of a C string (char *) variable


   The program below insists that you enter something for the -i option,
   the others all have default values...

   Some possible ways to test this program out:
     > getoptexample -v -n 100 -i hello
     > getoptexample -i somefile
     > getoptexample -x 100 -n 200 -i blah
*/


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

int main(int argc, char **argv) {
  char c;
  int verbose=0;
  int n=0;
  int foo=0;
  char *filename = NULL;

  while ((c=getopt(argc,argv,"vn:x:i:"))>=0) {
    switch(c) {
    case 'v':
      verbose=1; break;
    case 'n':
      n = atoi(optarg); break;
    case 'x':
      foo = atoi(optarg); break;
    case 'i':
      filename = optarg; break;
    case '?':  /* invalid option - getopt returns a '?' */
      exit(1);
    }
  }

  if (filename==NULL) {
    fprintf(stderr,"input file name must be specified!\n");
    exit(1);
  }

  printf("verbose is %s\n",(verbose?"on":"off"));
  printf("n is %d\n",n);
  printf("foo is %d\n",foo);
  printf("Filename is : %s\n",filename);
  return(0);
}