initscripts: Implement storing PIDs in loadproc

Some programs do not write their own PID files any more, but since our
initscripts heavily rely on those, this extension allows to store it
easily.

Signed-off-by: Daniel Weismüller <daniel.weismueller@ipfire.org>

src/initscripts/system/functions

@@ -446,6 +446,7 @@ loadproc()
 	local pidfile=""
 	local forcestart=""
 	local nicelevel=""
+	local pid
 
 # This will ensure compatibility with previous LFS Bootscripts
 	if [ -n "${PIDFILE}" ];	then
@@ -521,12 +522,19 @@ loadproc()
 		(
 			${cmd} &>/dev/null
 		) &
+		pid="$!"
 		evaluate_retval
 	else
 		${cmd}
+		pid="$!"
 		evaluate_retval # This is "Probably" not LSB compliant, but required to be compatible with older bootscripts
 	fi
 
+	# Write the pidfile
+	if [ -n "${pid}" -a -n "${pidfile}" ]; then
+		echo "${pid}" > "${pidfile}"
+	fi
+
 	return 0
 }