Why does a read-only open of a named pipe block?

Question

I\'ve noticed a couple of oddities when dealing with named pipes (FIFOs) under various flavors of UNIX (Linux, FreeBSD and MacOS X) using Python. The first, and perhaps mos

Answer 1

That's just the way it's defined. From the Open Group page for the open() function

O_NONBLOCK

    When opening a FIFO with O_RDONLY or O_WRONLY set: If O_NONBLOCK is
    set:

        An open() for reading only will return without delay. An open()
        for writing only will return an error if no process currently
        has the file open for reading.

    If O_NONBLOCK is clear:

        An open() for reading only will block the calling thread until a
        thread opens the file for writing. An open() for writing only
        will block the calling thread until a thread opens the file for
        reading.