Python Popen() is blocking

Question

I want to write a little python script to automate Jekyll blog creation, but popen() seems to block and not call asynchronously.

The expected behavior would be:

1. Start jekyll serve --livereload asynchronously
2. Start firefox-esr http://127.0.0.1:4000 async and wait for it(, or synchronously, this is not relevant in my use case)
3. After termination of firefox, terminate Jekyll too.

jekyll = subprocess.Popen(['jekyll', 'serve', '--livereload'])
print('This never gets displayed')
time.sleep(3)
firefox = subprocess.Popen(['firefox-esr', 'http://127.0.0.1:4000'])
firefox.wait()
jekyll.terminate()

But this only starts Jekyll and outputs its stdout to the terminal.

This problem only appears with Jekyll. ping or any other command/program i tried work fine.

Any ideas on what I did wrong?

Answer 1

If you are on Linux, you can create a simple bash script for it.

#!/bin/bash

jekyll serve --livereload & 
sleep 5
firefox-esr http://127.0.0.1:4000 &>/dev/null


pid=$(pgrep firefox-esr)

while :
do
    sleep 5
    if [ -z  "$pid" ]
    then
        pkill ruby 2>/dev/null
        echo "Killed jekyll"
        break
    fi
done

Give this file execution permissions with

chmod +x filename.sh

Then run this bash script with

./filename.sh &

This will make your script run in the background.