[英]Python subprocess: Why does stdin=PIPE change the output of some commands?
如果使用stdin進行管道傳輸,則某些交互式命令的輸出將有所不同。 這是為什么?
下面我測試subprocess.Popen在3個不同的命令上打開和關閉stdin。
碼:
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)
輸出:
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.
-----
對下面鏈接的問題的答案表明,某些程序試圖檢測它們是由人工運行還是由腳本運行。 是這樣嗎? 如果是這樣,他們如何在Windows上檢測到呢?
是的,如果您正在管道或重定向輸入,則某些程序的行為會有所不同。 您可以像這樣檢測到它:
import sys
print sys.stdin.isattty() # True if it's a terminal, False if it's redirected
這在* nix以及Windows上均可使用。
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