从需要标准输入的子进程实时打印标准输出 [英] printing stdout in realtime from a subprocess that requires stdin

问题描述

这是这个问题的后续行动，但如果我愿意要将参数传递给 stdin 到 subprocess，我怎样才能实时获得输出?这是我目前拥有的；我还尝试用 subprocess 模块中的 call 替换 Popen，这只会导致脚本挂起.

This is a follow up to this question, but if I want to pass an argument to stdin to subprocess, how can I get the output in real time? This is what I currently have; I also tried replacing Popen with call from the subprocess module and this just leads to the script hanging.

from subprocess import Popen, PIPE, STDOUT
cmd = 'rsync --rsh=ssh -rv --files-from=- thisdir/ servername:folder/'
p = Popen(cmd.split(), stdout=PIPE, stdin=PIPE, stderr=STDOUT)
subfolders = '
'.join(['subfolder1','subfolder2'])
output = p.communicate(input=subfolders)[0]
print output

在我不必通过 stdin 的前一个问题中，我被建议使用 p.stdout.readline，那里没有空间可以传输任何内容标准输入.

In the former question where I did not have to pass stdin I was suggested to use p.stdout.readline, there there is no room there to pipe anything to stdin.

附录:这适用于转移，但我只在最后看到输出，我想在转移发生时查看转移的详细信息.

Addendum: This works for the transfer, but I see the output only at the end and I would like to see the details of the transfer while it's happening.

推荐答案

为了实时从子进程中获取标准输出，你需要准确地决定你想要什么行为；具体来说，您需要决定是要逐行处理输出还是逐字符处理，以及是要在等待输出时阻塞还是在等待时能够做其他事情.

In order to grab stdout from the subprocess in real time you need to decide exactly what behavior you want; specifically, you need to decide whether you want to deal with the output line-by-line or character-by-character, and whether you want to block while waiting for output or be able to do something else while waiting.

看起来它可能足以让您的情况以行缓冲方式读取输出，阻塞直到每个完整的行进入，这意味着 subprocess 提供的便利功能已经足够好:

It looks like it will probably suffice for your case to read the output in line-buffered fashion, blocking until each complete line comes in, which means the convenience functions provided by subprocess are good enough:

p = subprocess.Popen(some_cmd, stdout=subprocess.PIPE)
# Grab stdout line by line as it becomes available.  This will loop until 
# p terminates.
while p.poll() is None:
    l = p.stdout.readline() # This blocks until it receives a newline.
    print l
# When the subprocess terminates there might be unconsumed output 
# that still needs to be processed.
print p.stdout.read()

如果您需要写入进程的标准输入，只需使用另一个管道:

If you need to write to the stdin of the process, just use another pipe:

p = subprocess.Popen(some_cmd, stdout=subprocess.PIPE, stdin=subprocess.PIPE)
# Send input to p.
p.stdin.write("some input
")
p.stdin.flush()
# Now start grabbing output.
while p.poll() is None:
    l = p.stdout.readline()
    print l
print p.stdout.read()

Pace 另一个答案，不需要间接通过文件来将输入传递给子进程.

Pace the other answer, there's no need to indirect through a file in order to pass input to the subprocess.

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