Getting realtime output using subprocess

Question

I am trying to write a wrapper script for a command line program (svnadmin verify) that will display a nice progress indicator for the operation. This requires me to be abl

Answer 1

In Python 3.x the process might hang because the output is a byte array instead of a string. Make sure you decode it into a string.

Starting from Python 3.6 you can do it using the parameter encoding in Popen Constructor. The complete example:

process = subprocess.Popen(
    'my_command',
    stdout=subprocess.PIPE,
    stderr=subprocess.STDOUT,
    shell=True,
    encoding='utf-8',
    errors='replace'
)

while True:
    realtime_output = process.stdout.readline()

    if realtime_output == '' and process.poll() is not None:
        break

    if realtime_output:
        print(realtime_output.strip(), flush=True)

Note that this code redirects stderr to stdout and handles output errors.