Don't process unmodified files.

TODO

@@ -1,5 +1,4 @@
 ============
 *** TODO ***
 ============
- - File date comparison to avoid unnecessary processing
  - Manner to loop through files in directory

sssg.sh

@@ -65,7 +65,6 @@ function parse {
 
 function generate {
 	# create directories
-	rm -rf _site
 	for i in $(find . -type d -not -path "./_templates" \
 		-not -path "./_site" -not -path "./_templates/*" \
 		-not -path "./_site/*")
@@ -81,18 +80,21 @@ function generate {
 		"./_site/*")
 	do
 		file_path=${i:2}
-		if [ ${file_path: -4} == ".htm" ] ||
-			[ ${file_path: -4} == ".HTM" ] ||
-			[ ${file_path: -5} == ".html" ] ||
-			[ ${file_path: -5} == ".HTML" ]
+		if [ "$file_path" -nt "_site/$file_path" ]
 		then
-			# parse HTML/CSS files
-			parse $file_path
-		else
-			# files that don't need parsing
-			echo -n "Copying file to _site/$file_path ... "
-			cp $file_path _site/$file_path
-			echo "OK"
+			if [ ${file_path: -4} == ".htm" ] ||
+				[ ${file_path: -4} == ".HTM" ] ||
+				[ ${file_path: -5} == ".html" ] ||
+				[ ${file_path: -5} == ".HTML" ]
+			then
+				# parse HTML/CSS files
+				parse $file_path
+			else
+				# files that don't need parsing
+				echo -n "Copying file to _site/$file_path ... "
+				cp $file_path _site/$file_path
+				echo "OK"
+			fi
 		fi
 	done
 }