Question

如果stdin是管道传输，某些交互式命令会以不同方式输出。那是为什么？

下面我在3个不同的命令上测试subprocess.Popen，使用和不使用stdin管道。

的代码：

import subprocess, time


def run_command(command, enable_input):
    print 'command="{}", enable_input={}:'.format(command, enable_input)

    # Launch the process and set up pipes.
    if enable_input:
        stdin = subprocess.PIPE
    else:
        stdin = None
    child = subprocess.Popen(command, stdin=stdin)

    # Wait a second for output.
    time.sleep(1)

    # Terminate the child if it hasn't finished.
    if child.poll() == None:
        child.terminate()

    print '\n-----' # Print a separator


commands = ('cmd', 'python', 'timeout 1')
for command in commands:
    run_command(command, enable_input=False)
    run_command(command, enable_input=True)

的输出：

command="cmd", enable_input=False:
Microsoft Windows [Version 6.1.7601]
Copyright (c) 2009 Microsoft Corporation.  All rights reserved.

C:\>
-----
command="cmd", enable_input=True:
Microsoft Windows [Version 6.1.7601]
Copyright (c) 2009 Microsoft Corporation.  All rights reserved.

C:\>
-----
command="python", enable_input=False:
Python 2.7.3 (default, Apr 10 2012, 23:31:26) [MSC v.1500 32 bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>>
-----
command="python", enable_input=True:

-----
command="timeout 1", enable_input=False:

Waiting for 0 seconds, press a key to continue ...

-----
command="timeout 1", enable_input=True:
ERROR: Input redirection is not supported, exiting the process immediately.

-----

下面链接的问题的答案表明，一些程序试图检测它们是由人类还是脚本运行。这是这种情况吗？如果是这样，他们如何在Windows上检测到它？

Why does supplying stdin to subprocess.Popen cause what is written to stdout to change?

Answer 1

是的，如果您正在管道或重定向输入，某些程序的行为会有所不同。您可以像这样检测它：

import sys
print sys.stdin.isattty()   # True if it's a terminal, False if it's redirected

这适用于* nix以及Windows。

Python子进程：为什么stdin = PIPE会改变某些命令的输出？

1 个答案: