#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <pthread.h>
#include <unistd.h>
#include <time.h>

#define MAXTHREAD 5
#define FIRE 20

typedef struct msg {
pthread_t tnum;
} M;

/*global*/
pthread_cond_t alert = PTHREAD_COND_INITIALIZER;
pthread_mutex_t alertmtx = PTHREAD_MUTEX_INITIALIZER;
static M foo;
void *monitor(void *);
void *do_random(void *);

#define liveloop() {while (1) {sleep(1);}}

int main(void) {
int y = 0;
pthread_t monthread;
pthread_t t[MAXTHREAD];

                       srand(time(NULL));
                       if (pthread_create(&monthread,NULL,monitor,NULL) != 0) {perror("pthread_create()"); return -1;}
                       while (y < MAXTHREAD) {
                                             pthread_create(&t[y],NULL,do_random,NULL);
                                             y++;
                       }
                       liveloop();
}

 void *monitor(void *arg) {

               pthread_mutex_lock(&alertmtx);
               while (1) {
                         pthread_cond_wait(&alert,&alertmtx);
                         printf("Received notification from thread id: %d.\n",foo.tnum);
               }
               pthread_mutex_unlock(&alertmtx);
}
 
void *do_random(void *arg) {
int r;
time_t beg, end;
              pthread_detach(pthread_self());
              r = (int)(1 + rand() % FIRE);       
              end = beg = time(NULL);
              end += r;
              for (;;) {
                  while (end > beg) {
                        beg = time(NULL);
                        sleep(1);
                  }
                  pthread_mutex_lock(&alertmtx);
                  foo.tnum = pthread_self();
                  pthread_cond_signal(&alert);
                  end += r;
                  pthread_mutex_unlock(&alertmtx);
              }
}