Bash script to apply a regex to Ogg Vorbis tags, and rename the files to match the tags, showing a diff of what it changed.

vorbis-retag-regex.sh

#!/bin/bash

#
# Apply regular expressions to Ogg Vorbis tags and filenames.
# Run with -h for help.
# https://gist.github.com/Malvineous/966f56d2df95e8e9f16f362fadb1f91f
#

set -e

# Defaults
ALBUM_FIRST=0
FULL_ARTIST=0
DRYRUN=0
RENAME=1
TAG=1

function help() {
	echo "Apply regular expressions to Ogg Vorbis tags and filenames."
	echo ""
	echo "vorbis-retag-regex.sh [options] <regex> *.ogg"
	echo ""
	echo "  options:"
	echo "    -a  Rename files to show album first"
	echo "    -c  Don't truncate artist in filename at second comma"
	echo "    -n  Dry run/preview, don't modify or rename any files"
	echo "    -r  Don't rename files at all (e.g. if name is too long)"
	echo "    -t  Don't retag, just rename (i.e. apply regex to filename only)"
	echo ""
	echo "  regex: sed expression over multiline tags, blank (\"\") to leave tags unmodified, e.g."
	echo "    's/\(title=\).*/\1New title/'    <= Replace title with 'New title'"
	echo "    's/\(artist=\).*/\1New artist/'  <= Replace artist with 'New artist'"
	echo "    's/\(album=\).*/\1New album/'    <= Replace album with 'New album'"
	echo "    '/tracknumber/a date=2000'       <= Add new 'date=2000' tag after tracknumber tag"
	echo "    '/^year=/ { d }'                 <= Completely remove 'year' tag"
	echo "    's/^\([A-Z_][^=]\+\)=/\L&/'      <= Convert all tag names to lowercase"
	echo "    's/\(\( \(A\|At\|In\|Of\|On\|The\|For\|And\)\)\+ \)/\L\1/g'  <= Convert short words to lowercase"
	echo ""
	echo "  examples:"
	echo "    # Rename all files based on existing tags (dry run, no files changed)"
	echo "    ./vorbis-retag-regex.sh -n '' *.ogg"
	echo ""
	echo "    # Change album tag and rename files to match"
	echo "    ./vorbis-retag-regex.sh 's/\(album=\).*/\1My Songs/' *.ogg"
	echo ""
	echo "Last-modified dates on files are left unchanged."
}

if [ "$1" == "" ]; then
	help
	exit
fi

while true; do
	case "$1" in
		-a)
			ALBUM_FIRST=1
			shift
		;;
		-c)
			FULL_ARTIST=1
			shift
		;;
		-n)
			DRYRUN=1
			shift
		;;
		-r)
			RENAME=0
			shift
		;;
		-t)
			TAG=0
			shift
		;;
		-h)
			help
			exit
		;;
		*)
			break
		;;
	esac
done

REGEX=$1
shift

for I in "$@"; do
	T_ORIG=`vorbiscomment -e "$I"`

	# Get new tags
	if [ "$REGEX" != "" ]; then
		T_NEW=`echo "$T_ORIG" | sed "$REGEX"`
	else
		T_NEW="$T_ORIG"
	fi

	# Get new name
	TAGS=`echo "$T_NEW" | sed 'y|/|⁄|'`
	TITLE=`echo "$TAGS" | grep -i -e '^title=' | cut -d= -f2`
	ARTIST=`echo "$TAGS" | grep -i -e '^artist=' | cut -d= -f2`
	if [ $FULL_ARTIST -eq 0 ]; then
		# Chop off the artist at the second comma, so if multiple artists are
		# specified, only the first two end up in the filename in order to stop them
		# from becoming too long and hitting filename length limits.
		ARTIST=`echo "$ARTIST" | sed 's/^\([^,]*,[^,]*\),.*$/\1/'`
	fi
	ALBUM=`echo "$TAGS" | grep -i -e '^album=' | cut -d= -f2`
	TRACK=`echo "$TAGS" | grep -i -e '^tracknumber=' | cut -d= -f2`
	if [ "$TRACK" == "" ]; then
		TRACK=0
		TRACKZ=00
	else
		TRACKZ=`printf %02d $[10#$TRACK]`
	fi
	if [ $ALBUM_FIRST -eq 0 ]; then
		F_NEW="${ARTIST} - ${ALBUM} - ${TRACKZ} - ${TITLE}.ogg"
	else
		F_NEW="${ALBUM} - ${TRACKZ} - ${ARTIST} - ${TITLE}.ogg"
	fi

	if [ "$TITLE" == "" ]; then
		echo "ERROR: Missing title tag: $I" > /dev/stderr
		continue
	fi
	if [ "$ARTIST" == "" ]; then
		echo "ERROR: Missing artist tag: $I" > /dev/stderr
		continue
	fi
	if [ "$ALBUM" == "" ]; then
		echo "ERROR: Missing album tag: $I" > /dev/stderr
		continue
	fi

	echo
	if [ "$I" != "$F_NEW" ] && [ "$RENAME" -eq 1 ]; then
		echo -e "\e[30;101m$I\e[0m"
		echo -e "\e[30;102m$F_NEW\e[0m"
	else
		echo -e "\e[30;104m$I\e[0m"
	fi

	if [ "$REGEX" != "" ] && [ $TAG -eq 1 ]; then
		diff --color=always -Nru <(echo "$T_ORIG") <(echo "$T_NEW") | tail -n +4
	fi

	if [ $DRYRUN -eq 0 ]; then
		if [ "$REGEX" != "" ] && [ $TAG -eq 1 ]; then
			echo "$T_NEW" | vorbiscomment -w "$I" _retag_out.ogg
			touch -r "$I" _retag_out.ogg && mv _retag_out.ogg "$I"
		fi
		if [ "$I" != "$F_NEW" ] && [ "$RENAME" -eq 1 ]; then
			mv "$I" "$F_NEW"
		fi
	fi
done