/**************************************************/
/* Multithreaded C program using the Pthread API  */
/* From Figure 5.5, Operating Systems Concepts,   */
/* Sixth Edition, Silberschatz, Galvin, and Gagne */
/*                                                */
/* To compile me in Linux type:                   */
/*    gcc -o chap5 chap5.c -lpthread              */
/**************************************************/

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

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

main(int argc, char *argv[])
{
  pthread_t tid; /* the thread identifier */
  pthread_attr_t attr; /* set of thread attributes */
  if (argc != 2) {
    fprintf(stderr, "usage:  a.out <integer value>\n");
    exit();
  }

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

  /* 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 upper = atoi(param);
  int i;
  sum=0;
  if (upper > 0) {
    for (i = 1; i <= upper; i++)
      sum += i;
  }
  pthread_exit(0);
}