Getting progress message from a subprocess

Question

I want to start a program which needs several minutes to complete. During this time I want to read the progress message of the program (which are printed on the stdout). The pro

Answer 1

Simplest is to call Popen with the keyword argument stdout=subprocess.PIPE.

p = subprocess.Popen(["ls"], stdout=subprocess.PIPE)
while True:
    line = p.stdout.readline()
    if not line:
        break
    print line

---

To see this in action, here are two sample scripts. Make them both in the same directory and run python superprint.py

printandwait.py:

import time
import sys
print 10
sys.stdout.flush()
time.sleep(10)
print 20
sys.stdout.flush()

superprint.py:

import subprocess
import sys
p = subprocess.Popen(["python printandwait.py"], shell=True, stdout=subprocess.PIPE)
while True:
    print "Looping"
    line = p.stdout.readline()
    if not line:
        break
    print line.strip()
    sys.stdout.flush()