subprocess.call() in Python

[senmeis]

Hi,

I want to use

subprocess.call(["ffmpeg", "-i", "test.mp4", "test.mp3"])

to make a media conversion.

Question: how can I redirect the console output so that this can be outputted with „print()“?

 

[Aussie Susan]

subprocess — Subprocess management

Source code: Lib/subprocess.py The subprocess module allows you to spawn new processes, connect to their input/output/error pipes, and obtain their return codes. This module intends to replace seve...

docs.python.org

 

[senmeis]

I tried the following two alternatives:



Alternative 1:

out = subprocess.run(["ffmpeg", "-i", "test.mp4", "test.mp3"], capture_output=True, text=True, shell=True)
print(out.stdout)

Alternative 2:

out = subprocess.check_output(["ffmpeg", "-i", "test.mp4", "test.mp3"], shell=True)
print(out.decode('utf-8'))

but both don’t print out anything. I just want to get the process info which comes from the console when ffmpeg is executed.

 

[Risso]

You can use the subprocess.PIPE to redirect the console output to your program. For example:

process = subprocess.Popen(["ffmpeg", "-i", "test.mp4", "test.mp3"], stdout=subprocess.PIPE, stderr=subprocess.STDOUT)

for line in iter(process.stdout.readline, b''):
    print(line.decode('utf-8').rstrip())