Run Python Script on File Addition – Automate with Command Line

• Check log files grep -i cron /var/log/syslog
• Add an empty line to the end of the crontab, This has been a known bug for ages, not sure if it is solved.
• Remove the 2>&1 from the command line until it works as designed. Any usefull errors are redirected to a file that is not created; effectively lost.
• Check if root received mail (eg. using mutt or in /var/spool/mail). Error messages from cron are sent to system email by default.

Also:

• Reconsider the 777 permissions as soon as possible. When running from root, 755 root:root should be sufficient to be able to check the logs from unprivileged user)
• Reconsider running the script from root, it is bad practise.

If filenames of the movies and subtitles files match and only the extensions differ, something like this should work.

#!/bin/bash

movie_dir=~/Movies
subtitle_dir=~/Subtitles
log=~/log.txt

for i in "$movie_dir"/*;do
    filname="${i%.*}"
    if [ ! -e "$subtitle_dir/$filename.srt" ];then
        echo "$filename" >> "$log"
    fi
done

EDIT For when each movie file is in it's own folder then try:

#!/bin/bash

movie_dir=~/Movies
subtitle_dir=~/Subtitles
log=~/log.txt

find "$movie_dir" -type f -name "*.mp4" -o -name "*.mkv" | while read i;do
    filename="$(basename "${i%.*}")"
    if [ ! -e "$subtitle_dir/$filename.srt" ];then
        echo "$filename" >> "$log"
    fi
done

This second way should work regardless of the movie folder structure, again as long as the filenames are the same.