Write opus track metadata extracted from filename

opustrackno.sh

#!/usr/bin/env bash

trim() {
        local var="$*"
        # remove leading whitespace characters
        var="${var#"${var%%[![:space:]]*}"}"
        # remove trailing whitespace characters
        var="${var%"${var##*[![:space:]]}"}"
        printf '%s' "$var"
}

cleanup() {
        rm -rf "${MYTMP}"
}

(( $# != 1 )) && exit 1

MYTMP=$(mktemp -qd)

trap 'cleanup' EXIT

write() {
        local name out buf nr

        name=$(basename "$1")
        out="${MYTMP}/${name}"
        buf=$(trim "$(printf '%s' "$name" | cut -d ' ' -f 1)")
        nr=${buf##+(0)} # remove potential padding

        if [[ $nr =~ ^[0-9]+$ ]]; then
                ffmpeg -i "$1" -acodec copy -metadata TRACKNUMBER="$nr" "$out"
                touch -r "$1" "$out"
                mv "$out" "$(dirname "$1")"
        fi
}

write "$(realpath -e "$1")"

#EOF