python - os.open() : no such device or address?

Question

我想尝试命名管道，所以我下载了一段代码并修改了它以进行测试:

fifoname = '/home/foo/pipefifo'                       # must open same name

def child( ):
    pipeout = os.open(fifoname, os.O_NONBLOCK|os.O_WRONLY)  
    # open fifo pipe file as fd
    zzz = 0
    while 1:
        time.sleep(zzz)
        os.write(pipeout, 'Spam %03d\n' % zzz)
        zzz = (zzz+1) % 5

def parent( ):
    pipein = open(fifoname, 'r')                 # open fifo as stdio object
    while 1:
        line = pipein.readline( )[:-1]            # blocks until data sent
        print 'Parent %d got "%s" at %s' % (os.getpid(), line, time.time( ))

if __name__ == '__main__':
    if not os.path.exists(fifoname):
        os.mkfifo(fifoname)                       # create a named pipe file
    if len(sys.argv) == 1:
        parent( )                                 # run as parent if no args
    else:
          child() 

我尝试运行脚本，它返回了这个错误:

pipeout = os.open(fifoname, os.O_NONBLOCK|os.O_WRONLY)     # open fifo pipe file as fd
OSError: [Errno 6] No such device or address: '/home/carrier24sg/pipefifo'

是什么导致了这个错误？ (我在 linux 中运行 python 2.6.5)

Answer 1

来自 man 7 fifo:

A process can open a FIFO in non-blocking mode. In this case, opening for read only will succeed even if no-one has opened on the write side yet, opening for write only will fail with ENXIO (no such device or address) unless the other end has already been opened.

所以你收到这个令人困惑的错误消息是因为你试图打开一个命名管道进行读取，而你正试图用一个非阻塞的open(2)打开它进行写入.

在您的具体示例中，如果您在 parent() 之前运行 child()，则会发生此错误。