#include <stdio.h>#include <unistd.h>#include <stdlib.h>#include <pthread.h>#define NUM_THREADS 6void *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);}