# This method if the files has no extentions. $ for file in *; do mv "$file" "$file.png"; done # This method if the files has extentions before. $ for …

One method is a bash *for loop*. Easy convert to .mp3 files: mkdir outputs/ for f in *.mp4; do ffmpeg -i "$f" "outputs/${f%.mp4}.mp3"; done For converting only .mp4 files: mkdir …