display usage info if required args not passed

rsync_tmbackup.sh

@@ -24,6 +24,9 @@ trap 'fn_terminate_script' SIGINT
 # -----------------------------------------------------------------------------
 # Small utility functions for reducing code duplication
 # -----------------------------------------------------------------------------
+fn_display_usage() {
+	fn_log_info "Usage : $(basename $0) <source> <destination> [exclude-pattern file]"
+}
 
 fn_parse_date() {
 	# Converts YYYY-MM-DD-HHMMSS to YYYY-MM-DD HH:MM:SS and then to Unix Epoch.
@@ -53,6 +56,11 @@ fn_expire_backup() {
 # -----------------------------------------------------------------------------
 # Source and destination information
 # -----------------------------------------------------------------------------
+#display usage information if required arguments are not passed
+if [[ "${#@}" -lt 2 ]]; then
+	fn_display_usage
+	exit 1
+fi
 
 SRC_FOLDER="${1%/}"
 DEST_FOLDER="${2%/}"