While loop resets a numeric variable in a Bash script [duplicate]

Answer 1

If you have bash 4.0 or later, use the globstar option instead of find:

shopt -s globstar
aux=0
for f in **/*.mp3; do
    # Just in case there is a directory name ending in '.mp3'
    [[ -f $f ]] || continue
    # Do something with $f
    echo "$(( ++aux ))"
done