#include <iostream>
#include <fstream>
#include <unistd.h>

#include <boost/interprocess/sync/file_lock.hpp>

using namespace std;
using namespace boost::interprocess;

int main(int argc, char *argv[]) {
  file_lock flock("lock");
    
  if (flock.try_lock()) cout << "Acquired lock" << endl;
  else {
    cout << "Could not acquire lock" << endl;
    return 1;
  }

  ifstream file("lock");

  // If you comment out the next line the lock stays active during the sleep.
  file.close(); // also closes lock

  sleep(30);

  return 0;
}