/* example of thread creation and termination

   This illustrates what happens if a main program does not
   bother to wait for threads to terminate.

   The behaviour depends on the first argument.
   See function usage() for details.

   Note that the example abuses the "void *" argument and return
   value of the thread body to hold an "int" value.  This is
   usually safe, since the size of a pointer is usually longer
   than or equal to the size of an integer.  However, a purist
   would create an integer variable to hold the value and pass
   the pointer.

 */

#define _XOPEN_SOURCE 500
#define _REENTRANT
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <pthread.h>
#include <stdio.h>
#include <values.h>
#include <errno.h>
#include <time.h>
#define NTHREADS 5
int index[NTHREADS];

void * thread_body (void *arg) {
  int *index = (int *) arg; 
  fprintf(stderr, "thread %d starts\n", *index); 
  sleep (1);
  fprintf(stderr, "thread %d exits\n", *index); 
  *index = *index * 10;
  return (void *) index;
}

void usage () {
   fprintf (stderr, "usage: example1 [ n | x | j | d ]\n"
   "n : use PTHREAD_CREATE_JOINABLE but don't wait\n"
   "j : use PTHREAD_CREATE_JOINABLE, with pthread_join\n"
   "d : use PTHREAD_CREATE_DETACHED, and don't wait\n"
   "x : use PTHREAD_CREATE_DETACHED, and wait 3 seconds\n");
}

int
main(int argc, char **argv) {
   int i, result;
   pthread_attr_t attrs;
   pthread_t thread[NTHREADS];
   void * value_ptr;

   if (argc != 2) { usage(); exit (-1);
   }

   pthread_attr_init (&attrs);

   /* use the command-line argument to decide whether to create
      the threads detached or joinable */
   if ((strcmp (argv[1], "d") == 0) || (strcmp (argv[1], "x") == 0))
      pthread_attr_setdetachstate (&attrs, PTHREAD_CREATE_DETACHED);

   /* create threads */
   for (i = 0; i < NTHREADS; i++) {
      index [i] = i;
      if ((result = pthread_create (
          &thread[i],  /* place to store the id of new thread */
          &attrs,      /* thread creation attributes */
          thread_body, /* function for thread to execute */
          (void *) &index[i]))) /* pass index as parameter */ {
         fprintf (stderr, "pthread_create: %d\n", result);
         exit (-1);
      }
   } 

   fprintf (stderr, "threads created\n"); 

   /* wait for the threads to complete */
   if (strcmp (argv[1], "j") == 0) {
      for (i = 0; i < NTHREADS; i++) {
         pthread_join (thread[i], &value_ptr);
         fprintf(stderr, "thread %d returned value %d\n", i,
           (int) value_ptr); 
      }
   }

   if (strcmp (argv[1], "x") == 0) {
      fprintf (stderr, "initial thread waiting 3 seconds\n");
      sleep (3);
   }
   fprintf (stderr, "initial thread exiting\n");
   exit (0);
}