/* sum.c - based on book example on page 173
 * The man page says to use "-pthread" to compile, as in:
 * gcc sum.c -pthread -o sum
 */
#include <pthread.h>
#include <stdio.h>

int sum;
void * runner (void * param);

int main(int argc, char *argv[])
{
  pthread_t tid;
  pthread_attr_t attr;

  if (argc != 2)
  {
    fprintf(stderr, "usage:  sum <integer>\n");
    return -1;
  }

  if (atoi (argv[1]) < 0)
  {
    fprintf(stderr, "%d must be >= 0\n", atoi(argv[1]));
    return -1;
  }

  pthread_attr_init(&attr);
  pthread_create(&tid, &attr, runner, argv[1]);
  pthread_join(tid, NULL);

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

void * runner(void *param)
{
  int i, upper = atoi(param);
  sum = 0;

  for (i = 1; i <= upper; ++i)
    sum += i;

  pthread_exit(0);
}