human
Complete this python program:
def installHandler(fd):
assistant
#Here is the Python program you requested.

    """Install a signal handler which will write a byte to C{fd} when
    I{SIGCHLD} is received.
    This is implemented by installing a SIGCHLD handler that does nothing,
    setting the I{SIGCHLD} handler as not allowed to interrupt system calls,
    and using L{signal.set_wakeup_fd} to do the actual writing.
    @param fd: The file descriptor to which to write when I{SIGCHLD} is
    received.
    @type fd: C{int}
    """
    if (fd == (-1)):
        signal.signal(signal.SIGCHLD, signal.SIG_DFL)
    else:
        def noopSignalHandler(*args):
            pass
        signal.signal(signal.SIGCHLD, noopSignalHandler)
        signal.siginterrupt(signal.SIGCHLD, False)
    return signal.set_wakeup_fd(fd)