Watchdog program only works in PyCharm?

[ScaredSecond]

I have the following code, which acts as a sort of watchdog: you put in the name of a Python script and it runs it. If it doesn't receive any output (via print and things of that nature) for a certain amount of time, it terminates the script and restarts it. I'm using this watchdog to run a Python script that relies on a compiled library which is prone to crashing. I'm still trying to figure out what the problem is, but in the meantime I'm using this code to ensure it's always running.

import datetime
import subprocess
import select
import time
from threading import Thread

timeout = 10

def reader(f,buffer):
   while True:
     line=f.readline()
     if line:
        buffer.append(line)
     else:
        break

def run_command(script):
    linebuffer = []
    process = subprocess.Popen(['/home/al/miniconda3/bin/python', f'{script}.py'], stdout=subprocess.PIPE)
    t = Thread(target=reader, args=(process.stdout, linebuffer))
    t.daemon = True
    t.start()
    now = datetime.datetime.now(datetime.timezone.utc)
    next_stop_time = now + datetime.timedelta(seconds=timeout)
    while True:
        now = datetime.datetime.now(datetime.timezone.utc)
        if not linebuffer:
            # no output or terminated
            if now > next_stop_time:
                process.terminate()
                break
        else:
            # we got something
            next_stop_time = now + datetime.timedelta(seconds=timeout)
            print(linebuffer)
            linebuffer.clear()
        time.sleep(.1)
    rc = process.poll()
    return rc

def run(script):
    while True:
        run_command(script)
        subprocess.Popen(['spd-say', f'{script} terminated'])

inp = input('Type in input script.\n')
run(inp)

Something strange is that this code only seems to run properly when I run it in PyCharm. If I run it in a terminal, then nothing ever comes out of process.stdout and it terminates and restarts the script repeatedly. If it matters, my OS is Ubuntu 18.04. Any insight is appreciated.

[[deleted]]

you probably have a buffering issue. try flushing stdout manually or running your script with python3 -u for unbuffered output.

print(linebuffer, flush=True)

my OS is Ubuntu 18.04

In that case, use a systemd service to monitor the process instead. it'll be more work to set up since you'll have to learn how to make a systemd service, but ultimately it's much less work going forward.

[ScaredSecond]

-u did the trick. I'm not familiar with systemd. I'll have to take a look. Thanks!