#include <sys/types.h>
#include <sys/shm.h>
#include <sys/ipc.h>
#include <time.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>

#define GLEN 4000
#define MLEN 2000
/* Note: prefix /dev/shm will be added automatically */
#define SHMFILE "meines"

int main() {

  int hdl;
  char *vp1;
  hdl = shm_open(SHMFILE, 
                 O_RDWR | O_CREAT, S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP);
  ftruncate(hdl, GLEN);
   vp1 = mmap(0, MLEN, PROT_READ | PROT_WRITE, MAP_SHARED, hdl, 0);

  /* return PID for checking */
  printf("My Pid is: %d\n", getpid());
  fflush(stdout);

  sleep(30);
  munmap(vp1, MLEN);
  shm_unlink(SHMFILE);
  return(0);
}