#include<errno.h>
#include<iostream>
#include<string>
#include<sys/types.h>
#include<sys/ipc.h>
#include<unistd.h>
#include<fcntl.h>
#include<semaphore.h>

using namespace std;


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


  sem_t* mysem;
  int oflag = O_CREAT;
  mode_t mode = 0644;
  const char semname[] = "/mysem";
  unsigned value = 1;
  int sts;

  mysem = sem_open(semname,oflag,mode,value);

  char c = cin.get();

  char buf[1];

  cout << "Process 1 checking semaphore..." << endl;
  sem_wait( mysem );
  cout << "Process 1 in critical section..." << endl;
  int fd = open( "file.txt", O_RDWR );
  read( fd, buf, 1 );
  cout << buf[0] << endl;
  cin.get();
  cin.get();
  close( fd );
  cout <<  "Unlock the remaphore" << endl;
  sem_post( mysem);

  cout << "Crticl section unlocked" << endl;
  sem_unlink( mysem );

  return 0;
}