#include <pthread.h>   /* POSIX 1003.1c threads */
#include <stdio.h>     /* standard input/output */

pthread_mutex_t mutex; /* Wechselseitiger Ausschluss */
pthread_cond_t cond;   /* Bedingungsvariable */
pthread_key_t key;     /* Thread-specifischer Datenschluessel */

int counter = 0;       /* Thread-Zaehler */
int printed = 0;       /* Hat Thread 0 bereits gedruckt? */

void print(void)
{
  char *string = (char*)pthread_getspecific(key);
  printf("%s", string);
}

void *thread(void *arg)
{
  int number; /* 0 = hello, 1 = world */
  
  pthread_mutex_lock(&mutex);
  number = counter; counter++;
  pthread_mutex_unlock(&mutex);
  
  pthread_setspecific(key, ((char**)arg)[number]);

  if (number == 0)
  {
    print(); 
    
    pthread_mutex_lock(&mutex);
    printed++;
    pthread_mutex_unlock(&mutex);
    
    pthread_cond_signal(&cond);
  }
  else
  {
    pthread_mutex_lock(&mutex);
    while (printed == 0) pthread_cond_wait(&cond, &mutex);
    pthread_mutex_unlock(&mutex);
    
    print();
  }

  return(0);
}

int main()
{
  char* strings[] = {"hello ", "world\n"};
  pthread_t thread1, thread2;
  
  pthread_mutex_init(&mutex, NULL);
  pthread_cond_init(&cond, NULL);
  pthread_key_create(&key, NULL);
  
  pthread_create(&thread1, NULL, thread, strings);
  pthread_create(&thread2, NULL, thread, strings);
  pthread_join(thread1, NULL);
  pthread_join(thread2, NULL);
  
  return(0);
}