systemd-stable/extras/rule_generator/rule_generator.functions

# functions used by the udev rule generator
#
# 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.

PATH='/sbin:/bin'

# Read a single line from file $1 in the $DEVPATH directory.
# The function must not return an error even if the file does not exist.
sysread() {
	local file="$1"
	[ -e "/sys$DEVPATH/$file" ] || return 0
	local value
	read value < "/sys$DEVPATH/$file" || return 0
	echo "$value"
}

sysreadlink() {
	local file="$1"
	[ -e "/sys$DEVPATH/$file" ] || return 0
	readlink -f /sys$DEVPATH/$file 2> /dev/null || true
}

# Return true if a directory is writeable.
writeable() {
	if ln -s test-link $1/.is-writeable 2> /dev/null; then
		rm -f $1/.is-writeable
		return 0
	else
		return 1
	fi
}

# Create a lock file for the current rules file.
lock_rules_file() {
	[ -e /dev/.udev/ ] || return 0

	RULES_LOCK="/dev/.udev/.lock-${RULES_FILE##*/}"

	retry=30
	while ! mkdir $RULES_LOCK 2> /dev/null; do
		if [ $retry -eq 0 ]; then
			 echo "Cannot lock $RULES_FILE!" >&2
			 exit 2
		fi
		sleep 1
		retry=$(($retry - 1))
	done
}

unlock_rules_file() {
	[ "$RULES_LOCK" ] || return 0
	rmdir $RULES_LOCK || true
}

# Choose the real rules file if it is writeable or a temporary file if not.
# Both files should be checked later when looking for existing rules.
choose_rules_file() {
	local tmp_rules_file="/dev/.udev/tmp-rules--${RULES_FILE##*/}"
	[ -e "$RULES_FILE" -o -e "$tmp_rules_file" ] || PRINT_HEADER=1

	if writeable ${RULES_FILE%/*}; then
		RO_RULES_FILE='/dev/null'
	else
		RO_RULES_FILE=$RULES_FILE
		RULES_FILE=$tmp_rules_file
	fi
}

# Return the name of the first free device.
raw_find_next_available() {
	local links="$1"

	local basename=${links%%[ 0-9]*}
	local max=-1
	for name in $links; do
		local num=${name#$basename}
		[ "$num" ] || num=0
		[ $num -gt $max ] && max=$num
	done

	local max=$(($max + 1))
	# "name0" actually is just "name"
	[ $max -eq 0 ] && return
	echo "$max"
}

# Find all rules matching a key (with action) and a pattern.
find_all_rules() {
	local key="$1"
	local linkre="$2"
	local match="$3"

	local search='.*[[:space:],]'"$key"'"\('"$linkre"'\)"[[:space:]]*\(,.*\|\\\|\)$'
	echo $(sed -n -e "${match}s/${search}/\1/p" $RO_RULES_FILE $RULES_FILE)
}