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

#include <pthread.h>

#define NUM_THREADS 6

void *thread_function(void *arg);

int main() {
  
  int res;
  pthread_t a_thread[NUM_THREADS];
  void *thread_result;
  int lots_of_threads;
  

  for(lots_of_threads = 0; lots_of_threads < NUM_THREADS; lots_of_threads++) {

    res = pthread_create(&(a_thread[lots_of_threads]), NULL, thread_function, (void *)lots_of_threads);
    if (res != 0) {
      perror("Thread creation failed");
      exit(EXIT_FAILURE);
    }
    /*    sleep(1); */
  }

  printf("Waiting for threads to finish...\n");
  for(lots_of_threads = NUM_THREADS - 1; lots_of_threads >= 0; lots_of_threads--) {
    res = pthread_join(a_thread[lots_of_threads], &thread_result);
    if (res == 0) {
      printf("Picked up a thread\n");
    } else {
      perror("pthread_join failed");
    }
  }

  printf("All done\n");
  
  exit(EXIT_SUCCESS);
}

void *thread_function(void *arg) {
    int my_number = (int)arg;
    int rand_num;

    printf("thread_function is running. Argument was %d\n", my_number);
    rand_num=1+(int)(9.0*rand()/(RAND_MAX+1.0));
    sleep(rand_num);
    printf("Bye from %d\n", my_number);
    
    pthread_exit(NULL);
}