diff --git a/scripts/_common.sh b/scripts/_common.sh
index 8078143..423ac1d 100644
--- a/scripts/_common.sh
+++ b/scripts/_common.sh
@@ -1,5 +1,12 @@
 #!/bin/bash
 
+CHECK_VAR () {	# Verifies that the variable is not empty.
+	# $1 = Variable to be checked
+	# $2 = Display text on error
+	test -n "$1" || (echo "$2" >&2 && false)
+}
+
+
 # Start (or other actions) a service,  print a log in case of failure and optionnaly wait until the service is completely started
 #
 # usage: ynh_systemd_action [-n service_name] [-a action] [ [-l "line to match"] [-p log_path] [-t timeout] [-e length] ]