Merging a Python script's subprocess' stdout and stderr while keeping them distinguishable

Question

I would like to direct a python script\'s subprocess\' stdout and stdin into the same file. What I don\'t know is how to make the lines from the two sources distinguishable?

Answer 1

tsk = subprocess.Popen(args,stdout=subprocess.PIPE,stderr=subprocess.STDOUT)

subprocess.STDOUT is a special flag that tells subprocess to route all stderr output to stdout, thus combining your two streams.

btw, select doesn't have a poll() in windows. subprocess only uses the file handle number, and doesn't call your file output object's write method.

to capture the output, do something like:

logfile = open(logfilename, 'w')

while tsk.poll() is None:
    line = tsk.stdout.readline()
    logfile.write(line)