Bash not terminating python script

Question

I'm trying to run a simple animated python script while bash executes some files. However the animation script isn't properly terminating once the bash script is done.

The python script works perfectly. If I use a different animation that runs natively in Bash, the bash script works. But if I get bash to run the python script, it runs forever?

Bash Script:

#!/usr/bin/env bash

# Don't leave animation running if files executed.
unset anim_pid
trap 'kill $anim_pid 2>/dev/null' EXT INT
# Get animation script
animation() {
      python "/home/solebay/Project/loading_animation.py"
}

animation & anim_pid=$!

# Scripts to execute
python "/home/solebay/Project/script_a" & pid1=$!
python "/home/solebay/Project/script_b" & pid2=$!

# wait for tasks to finish
wait $pid1 $pid2
kill $anim_pid 2>/dev/null

printf '\n *** End of script ***\n'

Python loading_animation.py:

#!/usr/bin/env python

import itertools
import threading
import time
import sys

# Please wait message
msg = "\nPlease wait a moment..."
for idx, i in enumerate(msg):
    if idx <= 19:
        sys.stdout.write(i)
        sys.stdout.flush()
        time.sleep(0.02)
    else:
       sys.stdout.write(i)
       sys.stdout.flush()
       time.sleep(0.6)
# Spinning part
for c in itertools.cycle(['|', '/', '-', '\\']):
    sys.stdout.write('\rPlease wait a moment... ' + c)
    sys.stdout.flush()
    time.sleep(0.1)

Ultimately it doesn't work and the animation mis-prints and then spins forever. Is this because I'm trying to use multithreading and then leaving threads open? Alternatively, are never-ending loading scripts a terrible idea?

a_guest · Accepted Answer · 2022-01-25 13:13:50Z

2

The problem is that you are putting the function in the background and then killing that function, but not the command that's running inside.

Instead you can invoke the script without wrapping it by a function:

python "/home/solebay/Project/loading_animation.py" &
anim_pid=$!

edited Jan 25, 2022 at 13:13

answered Jan 25, 2022 at 12:59

a_guest

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2 Comments

user1934428 Over a year ago

May I ask, why the variable anim_pid is not evaluated in the trap? How else can we pass variables to the trap? I guess putting them into the environment wouldn't help either.

a_guest Over a year ago

@user1934428 You are right, I was mistaken, it will be evaluated when invoked.

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