#include <stdio.h>
#include <sys/types.h>
#include <unistd.h>
#include <stdlib.h>

/* gcc ....  -lpthread */
#include <pthread.h>

#define CHILDREN 8

/* define three thread states */
#define RUNNING 0
#define DONE    1
#define JOINED  2

int done[ CHILDREN ];

struct thread_data {
 int t;  /* sleep time */
 int i;  /* index of this thread */
};

void * whattodo( void * arg );

int main()
{
 int i, rc;
 struct thread_data * t;
 pthread_t tid[ CHILDREN ];

 /* Create threads */
 for ( i = 0 ; i < CHILDREN ; i++ )
 {
   done[i] = RUNNING;
   t = (struct thread_data *)malloc( sizeof( struct thread_data ) );
   t->i = i;
   t->t = 10 + ( rand() % 21 );   /* in range [10,30] */
   printf( "MAIN: Next thread will nap for %d seconds.\n", t->t );

   rc = pthread_create( &tid[i], NULL, whattodo, t );
   if ( rc != 0 ) {
     perror( "Could not create the thread" );
   }
 }

#if 0
 /* Wait for threads to terminate */
 for ( i = 0 ; i < CHILDREN ; i++ ) {
   pthread_join( tid[i], NULL );       /* BLOCKING */
 }
#endif

 /* NONBLOCKING wait for threads to terminate */
 {
   int c = CHILDREN;
   while ( c > 0 )
   {
     for ( i = 0 ; i < CHILDREN ; i++ ) {
       if ( done[i] == DONE ) {
         pthread_join( tid[i], NULL );
         done[i] = JOINED;
         c--;
         printf( "MAIN: %d to go.\n", c );
       }
     }
     sleep( 1 );  /* parent does other work here ... */
   }
 }

 printf( "MAIN: All threads accounted for.\n" );
 return 0;
}

void * whattodo( void * arg )
{
 struct thread_data * t = (struct thread_data *)arg;
 printf( "THREAD %d: I'm gonna nap for %d seconds.\n", pthread_self(), t->t );
 sleep( t->t );
 printf( "THREAD %d: I'm awake now.\n", pthread_self() );
 done[ t->i ] = DONE;
 return NULL;
}