process.py 文件源码

def __pty_make_controlling_tty(self, tty_fd):
        '''This makes the pseudo-terminal the controlling tty. This should be
        more portable than the pty.fork() function. Specifically, this should
        work on Solaris. '''

        child_name = os.ttyname(tty_fd)

        # Disconnect from controlling tty. Harmless if not already connected.
        try:
            fd = os.open("/dev/tty", os.O_RDWR | os.O_NOCTTY)
            if fd >= 0:
                os.close(fd)
        # which exception, shouldnt' we catch explicitly .. ?
        except OSError:
            # Already disconnected. This happens if running inside cron.
            pass

        os.setsid()

        # Verify we are disconnected from controlling tty
        # by attempting to open it again.
        try:
            fd = os.open("/dev/tty", os.O_RDWR | os.O_NOCTTY)
            if fd >= 0:
                os.close(fd)
                raise Exception('Failed to disconnect from ' +
                    'controlling tty. It is still possible to open /dev/tty.')
        # which exception, shouldnt' we catch explicitly .. ?
        except OSError:
            # Good! We are disconnected from a controlling tty.
            pass

        # Verify we can open child pty.
        fd = os.open(child_name, os.O_RDWR)
        if fd < 0:
            raise Exception("Could not open child pty, " + child_name)
        else:
            os.close(fd)

        # Verify we now have a controlling tty.
        fd = os.open("/dev/tty", os.O_WRONLY)
        if fd < 0:
            raise Exception("Could not open controlling tty, /dev/tty")
        else:
            os.close(fd)