title: shm_open() doesn't create shared memory segment ipcs
body: <p>I got the following piece of C code which executes successfully:</p>
  
  <pre><code>...
  fd = shm_open(memory_package_name, O_CREAT | O_RDWR | O_EXCL , S_IRUSR | S_IWUSR);
  
  if (fd == -1) { //will fail if file already exists because of flag O_EXCL
      printf("\n shm_open() failed with error [%s]\n",strerror(errno));
      exit(EXIT_FAILURE);
  } else {
      printf("shm_open success\n");
  }
  ...
  </code></pre>
  
  <p>Using <code>ls -l /dev/shm</code> I see the file with <code>name memory_package_name</code> correctly created, but when I use <code>ipcs</code> it doesn't show any shared memory segment(s):</p>
  
  <pre><code>------ Shared Memory Segments --------
  key        shmid      owner      perms      bytes      nattch     status      
  
  ------ Semaphore Arrays --------
  key        semid      owner      perms      nsems     
  
  ------ Message Queues --------
  key        msqid      owner      perms      used-bytes   messages
  </code></pre>
  
  <p>Why?</p>