/**
 *
 * @author Gagne, Galvin, Silberschatz
 * Operating System Concepts  - Eighth Edition
 * Copyright John Wiley & Sons - 2009.
 */

#include <pthread.h>
#include <stdio.h>

int sum;			/* this data is shared by the thread(s) */

void *runner (void *param);	/* the thread */

int
main (int argc, char *argv[])
{
  pthread_t tid;		/* the thread identifier */
  pthread_attr_t attr;		/* set of attributes for the thread */

  if (argc != 2)
    {
      fprintf (stderr, "usage: a.out <integer value>\n");
      /*exit(1); */
      return -1;
    }

  if (atoi (argv[1]) < 0)
    {
      fprintf (stderr, "Argument %d must be non-negative\n", atoi (argv[1]));
      /*exit(1); */
      return -1;
    }

/* get the default attributes */
  pthread_attr_init (&attr);

/* create the thread */
  pthread_create (&tid, &attr, runner, argv[1]);

/* now wait for the thread to exit */
  pthread_join (tid, NULL);

  printf ("sum = %d\n", sum);
}

/**
 * The thread will begin control in this function
 */
void *
runner (void *param)
{
  int i, upper = atoi (param);
  sum = 0;

  if (upper > 0)
    {
      for (i = 1; i <= upper; i++)
	sum += i;
    }

  pthread_exit (0);
}