Read streaming input from subprocess.communicate()

Question

I\'m using Python\'s subprocess.communicate() to read stdout from a process that runs for about a minute.

How can I print out each line of that process

Answer 1

Adding another python3 solution with a few small changes:

1. Allows you to catch the exit code of the shell process (I have been unable to get the exit code while using the with construct)
2. Also pipes stderr out in real time

import subprocess
import sys
def subcall_stream(cmd, fail_on_error=True):
    # Run a shell command, streaming output to STDOUT in real time
    # Expects a list style command, e.g. `["docker", "pull", "ubuntu"]`
    p = subprocess.Popen(cmd, stdout=subprocess.PIPE, stderr=subprocess.STDOUT, bufsize=1, universal_newlines=True)
    for line in p.stdout:
        sys.stdout.write(line)
    p.wait()
    exit_code = p.returncode
    if exit_code != 0 and fail_on_error:
        raise RuntimeError(f"Shell command failed with exit code {exit_code}. Command: `{cmd}`")
    return(exit_code)