diff --git a/tools/fan_rpm_loop_test.sh b/tools/fan_rpm_loop_test.sh
index 3d38ea6..5c56878 100755
--- a/tools/fan_rpm_loop_test.sh
+++ b/tools/fan_rpm_loop_test.sh
@@ -84,5 +84,7 @@
     RunRpmSteps "${max_rpm}" "${min_rpm}"  1 30
 }
 
-return 0 2>/dev/null
-main "$@"
+if [ "$0" = "${BASH_SOURCE[0]}" ]; then
+    # not sourced, execute main function
+    main "$@"
+fi
diff --git a/tools/fan_rpm_loop_unittest.sh b/tools/fan_rpm_loop_unittest.sh
index 7ecde8b..e597d74 100755
--- a/tools/fan_rpm_loop_unittest.sh
+++ b/tools/fan_rpm_loop_unittest.sh
@@ -44,6 +44,8 @@
     echo "All tests completed."
 }
 
-return 0 2>/dev/null
-main "$@"
+if [ "$0" = "${BASH_SOURCE[0]}" ]; then
+    # not sourced, execute main function
+    main "$@"
+fi