将stdout和stderr与Python popen合并并检测stderr是否为空

Question

I want to run a sub process with popen that can send messages to both stdout and stderr, but that sub process will continue along it's merry way despite writing to stderr.

I want to stream stdout and stderr together so I get the output in the exact order it occurred (or was flushed I guess technically). Then, I want to log that full result set. BUT I also want to independently know if stderr is empty. If it is not, I'm going to throw an exception.

It is clear to me how I can get them separately, or merged together, but how can I perhaps do both?

Answer 1

First off I solved my actual use case in large part by digging further into the process producing the streams. I was using the MySQL client, and found the right combination of command line switches would solve the real goals. I'll leave that out since it's entirely specific to that situation.

Before I came upon that, however, I did find a very useful direction to explore - the use of the program "Tee" and / or a Python source equivalent. I did not try to implement it, but is seems like a method one could use to simultaneously collect the output from both stdout and stderr, while sending just stdout to another file descriptor. If the two outputs are not the same, then that would tell you if stderr was utilized.

Check out :

https://www.computerhope.com/unix/utee.htm

And :

Python subprocess get children's output to file and terminal?