grml-lock: run physlock with `-u` option only if it's supported

Closes grml/grml#87
Thanks: maximebuy for the bugreport

diff --git a/usr_bin/grml-lock b/usr_bin/grml-lock
index 673be73..ac05958 100755 (executable)
--- a/usr_bin/grml-lock
+++ b/usr_bin/grml-lock
@@ -44,7 +44,12 @@ and therefore might not work as intended." 7 70
 fi
 
 lock_desktop() {
-  sudo physlock -u "$USER"
+  # be backwards compatible, see https://github.com/grml/grml/issues/87
+  if physlock --help 2>&1 | grep -q -- '-u user' ; then
+    sudo physlock -u "$USER"
+  else
+    sudo physlock
+  fi
 }
 
 is_passwd_set() {