#include <stdio.h>
#include <semaphore.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>


main(int argc, char *argv[])
{
  sem_t *s;

  s = sem_open(argv[1], O_CREAT | O_RDWR, S_IRWXU | S_IRGRP | S_IROTH, 1);

  if( s == SEM_FAILED ){
    fprintf(stderr, "failed to open semaphore %s\n", argv[1]);
    exit(1);
  }

  fprintf(stderr, "waiting...\n");
  sem_wait( s );

  fprintf(stderr, "sleeping...\n");
  sleep(10);

  sem_post( s );
  fprintf(stderr, "ok now...\n");
}