python subprocess.call 输出不是交错的

问题描述

我有一个运行其他 shell 脚本的 python (v3.3) 脚本.我的 python 脚本还打印诸如关于运行脚本 X"和完成运行脚本 X"之类的消息.

I have a python (v3.3) script that runs other shell scripts. My python script also prints message like "About to run script X" and "Done running script X".

当我运行我的脚本时，我将 shell 脚本的所有输出与我的打印语句分开.我看到的是这样的:

When I run my script I'm getting all the output of the shell scripts separate from my print statements. I see something like this:

All of script X's output
All of script Y's output
All of script Z's output
About to run script X
Done running script X
About to run script Y
Done running script Y
About to run script Z
Done running script Z

我运行 shell 脚本的代码如下所示:

My code that runs the shell scripts looks like this:

print( "running command: " + cmnd )
ret_code = subprocess.call( cmnd, shell=True )
print( "done running command")

我写了一个基本的测试脚本并且做 *没有*看到这种行为.这段代码符合我的预期:

I wrote a basic test script and do *not* see this behaviour. This code does what I would expect:

print("calling")
ret_code = subprocess.call("/bin/ls -la", shell=True )
print("back")

知道为什么不交错输出的原因吗?

Any idea on why the output is not interleaved?

推荐答案

谢谢.这有效，但有一个限制 - 在命令完成之前您看不到任何输出.我从另一个问题(此处)中找到了答案，该问题使用popen 还可以让我实时查看输出.这是我最终的结果:

Thanks. This works but has one limitation - you can't see any output until after the command completes. I found an answer from another question (here) that uses popen but also lets me see the output in real time. Here's what I ended up with this:

import subprocess
import sys

cmd = ['/media/sf_git/test-automation/src/SalesVision/mswm/shell_test.sh', '4', '2']
print('running command: "{0}"'.format(cmd))  # output the command.
# Here, we join the STDERR of the application with the STDOUT of the application.
process = subprocess.Popen(cmd, bufsize=1, universal_newlines=True, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
for line in iter(process.stdout.readline, ''):
    line = line.replace('\n', '')
    print(line)
    sys.stdout.flush()
process.wait()                   #  Wait for the underlying process to complete.
errcode = process.returncode      #  Harvest its returncode, if needed.
print( 'Script ended with return code of: ' + str(errcode) )

这使用 Popen 并允许我查看被调用脚本的进度.

This uses Popen and allows me to see the progress of the called script.

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