diff --git a/CMakeLists.txt b/CMakeLists.txt
index 73192d8..3896d0f 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -25,4 +25,5 @@ add_executable(${PROJECT_NAME}
 	tiger.c
 	main.d
 	tiger.d
+	sums.d
 )
diff --git a/main.d b/main.d
index 775f68f..5e88514 100644
--- a/main.d
+++ b/main.d
@@ -17,31 +17,12 @@
 
 import std.stdio;
 import std.file;
-import tiger;
 import std.array;
 import std.getopt;
+import sums;
 
 mixin(import("tigersumConfig.d"));
 
-void calculateSums (in string[] parFiles, in string parCWD, bool parTiger2, string parFileMode, bool parBsdStyle) {
-	foreach (file_name; parFiles) {
-		const auto curr_path = parCWD ~ file_name;
-		File curr_file = File(curr_path, parFileMode);
-		if (!isDir(curr_path)) {
-			const string hash = tigerToString(getTiger(curr_file, parTiger2));
-			if (parBsdStyle) {
-				writefln("tiger (%s) = %s", file_name, hash);
-			}
-			else {
-				writefln("%s  %s", hash, file_name);
-			}
-		}
-		else {
-			writefln("tigersum: %s: is a directory", file_name);
-		}
-	}
-}
-
 int main (string[] parArgs) {
 	if (parArgs.length == 1)
 		return 0;
@@ -77,9 +58,13 @@ int main (string[] parArgs) {
 		"binary|b", &fileModeHandler,
 		"text|t", &fileModeHandler,
 		"tag", &bsd_style
+		//"quiet", &switch_quiet,
+		//"status", &switch_status,
+		//"warn|w", &switch_warn
 	);
 
 	if (check_mode) {
+		checkSums(args[1 .. $], working_dir, tiger_version == 2, file_mode);
 	}
 	else if (show_help) {
 		writefln("Usage: %s [OPTION]... [FILE]...", PROGRAM_NAME);
@@ -89,6 +74,10 @@ int main (string[] parArgs) {
 		writeln("  -t, --text          read in text mode (default)");
 		writefln("  -i n, --tiger=n     set the tiger version that should be used; valid values are 1 or 2, %d is default", TIGER_VERSION_DEF);
 		writeln();
+		//writeln("The following three options are useful only when verifying checksums:");
+		//writeln("      --quiet         don't print OK for each successfully verified file");
+		//writeln("      --status        don't output anything, status code shows success");
+		//writeln("  -w, --warn          warn about improperly formatted checksum lines");
 		writeln();
 		writeln("  -h, --help          display this help and exit");
 		writeln("  -v, --version       display version informations and exit");
diff --git a/sums.d b/sums.d
new file mode 100644
index 0000000..48101a1
--- /dev/null
+++ b/sums.d
@@ -0,0 +1,87 @@
+/*	tigersum - a command line utility to calculate the tiger hash from input.
+	Copyright (C) 2014  Michele "King_DuckZ" Santullo
+
+	This program is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
+
+	This program is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+	GNU General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+import std.regex;
+import std.stdio;
+import std.file : isDir;
+import std.conv;
+import std.string;
+import tiger;
+
+void calculateSums (in string[] parFiles, in string parCWD, bool parTiger2, string parFileMode, bool parBsdStyle) {
+	foreach (file_name; parFiles) {
+		const auto curr_path = parCWD ~ file_name;
+		File curr_file = File(curr_path, parFileMode);
+		if (!isDir(curr_path)) {
+			const string hash = tigerToString(getTiger(curr_file, parTiger2));
+			if (parBsdStyle) {
+				writefln("tiger (%s) = %s", file_name, hash);
+			}
+			else {
+				writefln("%s  %s", hash, file_name);
+			}
+		}
+		else {
+			writefln("tigersum: %s: is a directory", file_name);
+		}
+	}
+}
+
+bool checkSums (in string parFile, in string parCWD, bool parTiger2, string parFileMode) {
+	File curr_list = File(parFile, "r");
+	bool ret_val = true;
+	const auto reg_bsd = r"^tiger \((.+)\)\s*=\s*([a-fA-F0-9]{48})$";
+	const auto reg_normal = r"^([a-fA-F0-9]{48})\s+(.+)$";
+
+	foreach (line; curr_list.byLine()) {
+		auto m = match(line, reg_bsd);
+		int index_hash, index_file;
+		if (m) {
+			index_hash = 2;
+			index_file = 1;
+		}
+		else {
+			m = match(line, reg_normal);
+			index_hash = 1;
+			index_file = 2;
+		}
+
+		if (m) {
+			const string capt_filename = to!string(m.captures[index_file]);
+			writef("%s: ", capt_filename);
+
+			const string curr_path = parCWD ~ capt_filename;
+			File curr_file = File(curr_path, parFileMode);
+			const string curr_tiger = tigerToString(getTiger(curr_file, parTiger2));
+			const string check_tiger = to!string(m.captures[index_hash]).toLower;
+			if (check_tiger == curr_tiger)
+				writeln("OK");
+			else
+				writeln("FAILED");
+		}
+	}
+	return ret_val;
+}
+
+bool checkSums (in string[] parFiles, in string parCWD, bool parTiger2, string parFileMode) {
+	bool ret_val = true;
+	foreach (file_name; parFiles) {
+		const auto curr_path = parCWD ~ file_name;
+		ret_val &= checkSums(curr_path, parCWD, parTiger2, parFileMode);
+	}
+	return ret_val;
+}