Question

我在Unix环境中运行Python 2.7（在Ubuntu和OSX上测试）

我有以下程序：

使用os.open（）：

[脚本1]

import os

pipe_1_name = "pipe_1"
pipe_2_name = "pipe_2"
pipe_3_name = "pipe_3"


def set_connection():
    pipe_names = [pipe_1_name, pipe_2_name, pipe_3_name]
    for pipe_name in pipe_names:
        if os.path.exists(pipe_name):
            os.remove(pipe_name)
            os.mkfifo(pipe_name)
        else:
            os.mkfifo(pipe_name)

    pipe_1 = os.open(pipe_1_name, os.O_WRONLY)
    os.write(pipe_1, "server_message_0\n")

    pipe_2 = open(pipe_2_name, 'r')
    received = pipe_2.readline()[:-1]
    print "[0] Now processing if received is correct: " + received

    pipe_3 = open(pipe_3_name, 'r')
    received = pipe_3.readline()[:-1]
    print "[1] Now processing if received is correct: " + received

    print "Connection established."
    return pipe_1,pipe_2,pipe_3


def main():
    pipe_1, pipe_2, pipe_3 = set_connection()

    print str(pipe_1)
    print str(pipe_2)
    print str(pipe_3)

if __name__ == "__main__":
    main()

[脚本2]

import os

pipe_1_name = "pipe_1"
pipe_2_name = "pipe_2"
pipe_3_name = "pipe_3"


def get_connection():
    pipe_names = [pipe_1_name, pipe_2_name, pipe_3_name]
    for pipe_name in pipe_names:
        if not os.path.exists(pipe_name):
            raise Exception("Pipe "+pipe_name+" does not exist!")

    pipe_1 = open(pipe_1_name, 'r')
    received = pipe_1.readline()[:-1]
    print "[0] Now processing if received is correct: " + received

    pipe_2 = os.open(pipe_2_name, os.O_WRONLY)
    os.write(pipe_2, "client_message_0\n")

    pipe_3 = os.open(pipe_3_name, os.O_WRONLY)
    os.write(pipe_3, "client_message_1\n")

    print "Connection established."
    return pipe_1,pipe_2,pipe_3


def main():
    pipe_1, pipe_2, pipe_3 = get_connection()

    print str(pipe_1)
    print str(pipe_2)
    print str(pipe_3)

if __name__ == "__main__":
    main()

逻辑很简单：

[管1] 1.脚本1打开脚本2的写入管道。 2.脚本2从管道中读取。 [管2] 3.脚本2打开脚本1的写入管道。脚本1从管道中读取。 [管3] 5.脚本2打开脚本1的写入管道。 6.脚本1从管道中读取。

完全符合预期。

这是问题所在。我不想使用os.open（）。我希望接收一个文件对象并使用它来与管道接口。显然，这并非不可能，因为我可以从带有文件对象的管道中读取。但是，以下脚本不起作用。

没有os.open（）

[脚本1]

import os

pipe_1_name = "pipe_1"
pipe_2_name = "pipe_2"
pipe_3_name = "pipe_3"


def set_connection():
    pipe_names = [pipe_1_name, pipe_2_name, pipe_3_name]
    for pipe_name in pipe_names:
        if os.path.exists(pipe_name):
            os.remove(pipe_name)
            os.mkfifo(pipe_name)
        else:
            os.mkfifo(pipe_name)

    pipe_1 = open(pipe_1_name, 'w')
    pipe_1.write("server_message_0\n")

    pipe_2 = open(pipe_2_name, 'r')
    received = pipe_2.readline()[:-1]
    print "[0] Now processing if received is correct: " + received

    pipe_3 = open(pipe_3_name, 'r')
    received = pipe_3.readline()[:-1]
    print "[1] Now processing if received is correct: " + received

    print "Connection established."
    return pipe_1,pipe_2,pipe_3


def main():
    pipe_1, pipe_2, pipe_3 = set_connection()

    print str(pipe_1)
    print str(pipe_2)
    print str(pipe_3)

if __name__ == "__main__":
    main()

[脚本2]

import os

pipe_1_name = "pipe_1"
pipe_2_name = "pipe_2"
pipe_3_name = "pipe_3"


def get_connection():
    pipe_names = [pipe_1_name, pipe_2_name, pipe_3_name]
    for pipe_name in pipe_names:
        if not os.path.exists(pipe_name):
            raise Exception("Pipe "+pipe_name+" does not exist!")

    pipe_1 = open(pipe_1_name, 'r')
    received = pipe_1.readline()[:-1]
    print "[0] Now processing if received is correct: " + received

    pipe_2 = open(pipe_2_name, 'w')
    pipe_2.write("client_message_0\n")

    pipe_3 = open(pipe_3_name, 'w')
    pipe_3.write("client_message_1\n")

    print "Connection established."
    return pipe_1,pipe_2,pipe_3


def main():
    pipe_1, pipe_2, pipe_3 = get_connection()

    print str(pipe_1)
    print str(pipe_2)
    print str(pipe_3)

if __name__ == "__main__":
    main()

他们看起来一样，不是吗？唯一的区别是我如何打开fifo。而不是os.open(pipe_name,os.O_WRONLY)我使用pipe = open(pipe_name, 'w')。

第二组脚本中发生了什么，不使用os.open（），脚本1在pipe_2 = open(pipe_2_name, 'r')阻塞，而脚本2在pipe_2 = open(pipe_2_name, 'w')阻塞。

为什么会这样？

对不起文字墙。我对这个问题感到很困惑。

Answer 1

第二组脚本中发生了什么，不使用的脚本 os.open（），脚本1在07-10 13:08:12.113 D/dalvikvm( 2154): GREF has increased to 2001 07-10 13:08:12.113 W/dalvikvm( 2154): JNI global reference table (0xb9059ae0) dump: 07-10 13:08:12.113 W/dalvikvm( 2154): Last 10 entries (of 2001): 07-10 13:08:12.113 W/dalvikvm( 2154): 2000: 0xab294a58 android.widget.RelativeLayout$LayoutParams 07-10 13:08:12.113 W/dalvikvm( 2154): 1999: 0xab2949f8 mono.android.view.View_OnClickListenerImplementor 07-10 13:08:12.113 W/dalvikvm( 2154): 1998: 0xab294828 android.widget.RelativeLayout$LayoutParams 07-10 13:08:12.113 W/dalvikvm( 2154): 1997: 0xab294458 android.widget.ImageView 07-10 13:08:12.113 W/dalvikvm( 2154): 1996: 0xab294320 android.widget.RelativeLayout$LayoutParams 07-10 13:08:12.113 W/dalvikvm( 2154): 1995: 0xab2942c0 mono.android.view.View_OnClickListenerImplementor 07-10 13:08:12.113 W/dalvikvm( 2154): 1994: 0xab293cc8 android.widget.TextView 07-10 13:08:12.113 W/dalvikvm( 2154): 1993: 0xab293658 android.widget.RelativeLayout 07-10 13:08:12.113 W/dalvikvm( 2154): 1992: 0xab290998 android.widget.RelativeLayout$LayoutParams 07-10 13:08:12.113 W/dalvikvm( 2154): 1991: 0xab290860 android.widget.RelativeLayout$LayoutParams 07-10 13:08:12.113 W/dalvikvm( 2154): Summary:处阻塞，而脚本2在pipe_2 = open(pipe_2_name, 'r')处阻塞。

不，脚本2在pipe_2 = open(pipe_2_name, 'w')处阻止。

为什么会发生这种情况？

这是因为脚本1的received = pipe_1.readline()[:-1]导致写入的消息以固定大小的块（通常为4096或8192字节）进行缓冲，因此open(pipe_1_name, 'w')尚未向管道写入任何内容，而只是到缓冲区，脚本2没有任何东西可读。请参阅open()以及How often does python flush to a file?

要解决此问题，由于您的消息是完整的行，因此只需使用行缓冲，e。克。

pipe_1.write("server_message_0\n")

（以及其他写管道）。

理解Python

1 个答案: