--- orig/shell-tools
+++ mod/shell-tools
@@ -21,6 +21,42 @@
 # Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 #
 
+# Print verbose message to standard output
+# Has to be enabled by enable_verbose
+verbose ()
+{
+    :
+}
+
+# Enable verbose function outpug
+enable_verbose ()
+{
+    verbose ()
+    {
+	local message="$@"
+
+	echo "${message}"
+    }
+}
+
+# Print debugging message to standard error
+# Has to be enabled using enable_debug function
+debug ()
+{
+    :
+}
+
+# Enable debug function outpug
+enable_debug ()
+{
+    debug ()
+    {
+	local message="$@"
+
+	echo >&2 "$(basename $0): ${message}"
+    }
+}
+
 # Print warning message to standard error
 warn ()
 {
