Sorts a Bandcamp discography by release date

bandcamp_discography.sh

#!/bin/bash
# Utility for Bandcamp discographies
# Copyright (C) 2016 Christoph "criztovyl" Schulz
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
if [[ "$1" =~ ^-{0,2}h(elp)?$ ]]; then
    echo "Usage: $0 [USER] [ACTION]" >&2
    echo " USER: " >&2
    echo "    bandcamp artist domain, i.e. \"shirobon\" for \"https://shirobon.bandcamp.com\"" >&2
    echo " ACTION: " >&2
    echo "    releases: list releases (sorted)" >&2
    echo "    covers: download all release covers to current folder (artist-album.jpg)" >&2
    echo "    urls: display releases urls" >&2
    echo "    if invalid falls back to releases" >&2
    echo
    echo "Generates status output (on stderr), disable by setting BC_ODS to any value." >&2
    echo "Artist page has own domain? Look at OpenGraph url prop: I.e. for J-M-R try $ curl https://j-m-r.net | grep \"og:url\" " >&2
    exit 0
fi

CURL="curl"
[ "$BC_ODS" ] && CURL=$CURL" -s"

[ -z "$1" ] && { echo "No user given!" >&2; exit 2; }

user=$1
url="https://$user.bandcamp.com"

urls=`$CURL -L "$url""/music" | perl -ne '/<a href="(\/(track|album).*?)"/ && print "'$url'".$1."\n"'`
[ -z "$urls" ] && { echo "No releases found." >&2; exit 1; }

case $2 in
    "urls")
        echo $urls
        ;;
    "covers")
        re='\s*artFullsizeUrl: "(.*)"'
        for url in $urls
        do
            echo $url
            slug=${url##*/}
            [[ `curl -L $url | grep artFullsizeUrl` =~ $re ]] && wget -O $user"-"$slug.${BASH_REMATCH[1]##*.} ${BASH_REMATCH[1]}
        done
        ;;
    *|"releases")
        # all-in-one command to let curl reuse connection
        $CURL $urls |
        grep "released " |
        perl -ne '/(.*), released (\d{2}) (\w{3})\w* (\d{4})/ && print $4." ".$3." ".$2.": ".$1."\n"' |
        LANG=en sort -t" " -k1n,1 -k2M,2 -k3n,3
        ;;
esac