systemd/extras/rule_generator/write_cd_rules

#!/bin/sh -e

# This script is run if an optical drive lacks a rule for persistent naming.
#
# It adds symlinks for optical drives based on the device class determined
# by cdrom_id and used ID_PATH to identify the device.
#
# (C) 2006 Marco d'Itri <md@Linux.IT>
#
# 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 version 2 of the License.

RULES_FILE="/etc/udev/rules.d/70-persistent-cd.rules"

. /lib/udev/rule_generator.functions

find_next_available() {
	raw_find_next_available "$(find_all_rules 'SYMLINK+=' "$1")"
}

write_rule() {
	local match="$1"
	local link="$2"
	local comment="$3"

	{
	if [ "$PRINT_HEADER" ]; then
		PRINT_HEADER=
		echo "# This file was automatically generated by the $0"
		echo "# program, probably run by the cd-aliases-generator.rules rules file."
		echo "#"
		echo "# You can modify it, as long as you keep each rule on a single line"
		echo "# and set the \$GENERATED variable."
		echo ""
	fi

	[ "$comment" ] && echo "# $comment"
	echo "$match, SYMLINK+=\"$link\", ENV{GENERATED}=\"1\""
	} >> $RULES_FILE
	SYMLINKS="$SYMLINKS $link"
}

if [ -z "$DEVPATH" ]; then
	echo "Missing \$DEVPATH." >&2
	exit 1
fi
if [ -z "$ID_CDROM" ]; then
	echo "$DEVPATH is not a CD reader." >&2
	exit 1
fi

if [ "$1" ]; then
	METHOD="$1"
else
	METHOD='by-path'
fi

case "$METHOD" in
	by-path)
	if [ -z "$ID_PATH" ]; then
		echo "$DEVPATH not supported by path_id. by-id may work." >&2
		exit 1
	fi
	RULE="ENV{ID_PATH}==\"$ID_PATH\""
	;;

	by-id)
	if [ "$ID_SERIAL" ]; then
		RULE="ENV{ID_SERIAL}==\"$ID_SERIAL\""
	elif [ "$ID_MODEL" -a "$ID_REVISION" ]; then
		RULE="ENV{ID_MODEL}==\"$ID_MODEL\", ENV{ID_REVISION}==\"$ID_REVISION\""
	else
		echo "$DEVPATH not supported by ata_id. by-path may work." >&2
		exit 1
	fi
	;;

	*)
	echo "Invalid argument (must be either by-path or by-id)." >&2
	exit 1
	;;
esac

# Prevent concurrent processes from modifying the file at the same time.
lock_rules_file

# Check if the rules file is writeable.
choose_rules_file

link_num=$(find_next_available 'cdrom[0-9]*')

match="ENV{ID_CDROM}==\"?*\", $RULE"

comment="$ID_MODEL ($ID_PATH)"

	write_rule "$match" "cdrom$link_num" "$comment"
[ "$ID_CDROM_CD_R" -o "$ID_CDROM_CD_RW" ] && \
	write_rule "$match" "cdrw$link_num"
[ "$ID_CDROM_DVD" ] && \
	write_rule "$match" "dvd$link_num"
[ "$ID_CDROM_DVD_R" -o "$ID_CDROM_DVD_RW" -o "$ID_CDROM_DVD_RAM" ] && \
	write_rule "$match" "dvdrw$link_num"

unlock_rules_file

echo $SYMLINKS

exit 0