shm-3b.c

#include <sys/mman.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdio.h>

int main (void)
{
  char buffer[42];
  int file = open ("test.txt", O_RDONLY, 0444);
  lseek (file, 0, SEEK_SET);
  read (file, buffer, 42);
  close (file);
  printf ("%s\n", buffer);
  return 0;
}