#include <iostream>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/sem.h>
#include <cstdlib>
#include <cstring>
#include <errno.h>

using namespace std;

static void usage(const char *progname);

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

  if (argc != 2)
    usage(argv[0]);

  int key = atoi(argv[1]);

  int semid = semget(key, 1, 0660 );

  if (semid == -1) {
    cerr << "Error abrir el semaforo: " <<
      strerror(errno) << endl;
    return EXIT_FAILURE;
  }

  for (;;) {
    struct sembuf op[1];

    op[0].sem_num = 0;
    op[0].sem_op = -1;
    op[0].sem_flg = 0;

    cout << "Esperando para imprimir" << endl;
    semop(semid, op, 1);
    cout << "Impresion lista" << endl;
  }

  return EXIT_SUCCESS;
}

static void usage(const char *progname) {
  cerr << "Uso: " << progname << " <semkey> "
       << endl;
  exit(EXIT_FAILURE);
}