How do I use a named pipe?

To use the pipe, you open it like a normal file, and use read()
and write() just as though it was a plain pipe.

However, the open() of the pipe may block. The following rules
apply:

• 
  
  If you open for both reading and writing (O_RDWR), then the open
  will not block.
  
  
• 
  
  If you open for reading (O_RDONLY), the open will block until
  another process opens the FIFO for writing, unless O_NONBLOCK is
  specified, in which case the open succeeds.
  
  
• 
  
  If you open for writing O_WRONLY, the open will block until
  another process opens the FIFO for reading, unless O_NONBLOCK is
  specified, in which case the open fails.
  

When reading and writing the FIFO, the same considerations apply as for
regular pipes and sockets, i.e. read() will return EOF when all
writers have closed, and write() will raise SIGPIPE when
there are no readers. If SIGPIPE is blocked or ignored, the call
fails with EPIPE.