title: F_GETPIPE_SZ returns -1 in C
body: <p>Why would F_GETPIPE_SZ return -1? It sounds like an error, but I can't find any mention of what error it is, or, more importantly, what I'm supposed to do to not get the error.</p>
  
  <p>I'm running Raspbian on a Raspberry Pi, for what it's worth. I haven't tried the code on my desktop Debian yet. As far as I can tell, I'm following the textbook F_GETPIPE_SZ example. Am I missing something?</p>
  
  <pre><code>#define _GNU_SOURCE
  #include &lt;stdio.h&gt;
  #include &lt;fcntl.h&gt;
  #include &lt;sys/stat.h&gt;
  #include &lt;unistd.h&gt;
  
  int main(int argc, char **argv)
  {
    int fd, pipesize;
    fd = mkfifo("/tmp/audio-fifo",0666);
    //  fcntl(fd, F_SETPIPE_SZ, 4096);
    pipesize = fcntl(fd, F_GETPIPE_SZ);
    printf("Pipe size: %d\n", pipesize);
    return 0;
  }
  </code></pre>