How can I capture the stdout output of a child process?

Question

I\'m trying to write a program in Python and I\'m told to run an .exe file. When this .exe file is run it spits out a lot of data and I need a certain line printed out to th

Answer 1

@Paolo's solution is perfect if you are interested in printing output after the process has finished executing. In case you want to poll output while the process is running you have to do it this way:

process = subprocess.Popen(cmd, stdout=subprocess.PIPE)

while True:
    out = process.stdout.readline(1)
    if out == '' and process.poll() != None:
        break
    if out.startswith('myline'):
        sys.stdout.write(out)
        sys.stdout.flush()

Answer 2

Something like this:

import subprocess
process = subprocess.Popen(["yourcommand"], stdout=subprocess.PIPE)
result = process.communicate()[0]