将标准输出从 subprocess.Popen 保存到文件，并将更多内容写入文件 [英] Saving stdout from subprocess.Popen to file, plus writing more stuff to the file

问题描述

我正在编写一个 python 脚本，它使用 subprocess.Popen 来执行两个程序(来自已编译的 C 代码)，每个程序都会产生标准输出.该脚本获取该输出并将其保存到文件中.因为输出有时大到足以压倒 subprocess.PIPE，导致脚本挂起，所以我将 stdout 直接发送到日志文件.我想让我的脚本在文件的开头和结尾以及两个 subprocess.Popen 调用之间写一些东西.但是，当我查看日志文件时，我从脚本写入日志文件的所有内容都放在文件的顶部，然后是所有可执行的标准输出.如何将添加的文本交错到文件中?

I'm writing a python script that uses subprocess.Popen to execute two programs (from compiled C code) which each produce stdout. The script gets that output and saves it to a file. Because the output is sometimes large enough to overwhelm subprocess.PIPE, causing the script to hang, I send the stdout directly to the log file. I want to have my script write something to the beginning and end of the file, and between the two subprocess.Popen calls. However, when I look at my log file, anything I wrote to the log file from the script is all together at the top of the file, followed by all the executable stdout. How can I interleave my added text to the file?

def run(cmd, logfile):
    p = subprocess.Popen(cmd, shell=True, universal_newlines=True, stdout=logfile)
    return p

def runTest(path, flags, name):
    log = open(name, "w")
    print >> log, "Calling executable A"
    a_ret = run(path + "executable_a_name" + flags, log)
    print >> log, "Calling executable B"
    b_ret = run(path + "executable_b_name" + flags, log)
    print >> log, "More stuff"
    log.close()

日志文件有:调用可执行文件 A调用可执行文件 B更多东西[...来自两个可执行文件的标准输出...]

The log file has: Calling executable A Calling executable B More stuff [... stdout from both executables ...]

例如，在调用 Popen 之后，有没有办法可以将 A 的标准输出刷新到日志中?还有一件可能相关的事情:可执行文件 A 开始，然后在 B 上挂起，在 B 打印内容并完成之后，A 然后打印更多内容并完成.

Is there a way I can flush A's stdout to the log after calling Popen, for example? One more thing that might be relevant: Executable A starts then pends on B, and after B prints stuff and finishes, A then prints more stuff and finishes.

我在 RHE Linux 上使用 Python 2.4.

I'm using Python 2.4 on RHE Linux.

推荐答案

您可以在每个 Popen 对象上调用 .wait() 以确保它已完成，然后调用 log.flush().也许是这样的:

You could call .wait() on each Popen object in order to be sure that it's finished and then call log.flush(). Maybe something like this:

def run(cmd, logfile):
    p = subprocess.Popen(cmd, shell=True, universal_newlines=True, stdout=logfile)
    ret_code = p.wait()
    logfile.flush()
    return ret_code

如果您需要与外部函数中的 Popen 对象进行交互，您可以将 .wait() 调用移到那里.

If you need to interact with the Popen object in your outer function you could move the .wait() call to there instead.

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