diff --git a/native/dicttoolkit/NativeFileList.mk b/native/dicttoolkit/NativeFileList.mk
index b6be9c5..2ba9859 100644
--- a/native/dicttoolkit/NativeFileList.mk
+++ b/native/dicttoolkit/NativeFileList.mk
@@ -15,7 +15,9 @@
 LATIN_IME_DICT_TOOLKIT_MAIN_SRC_FILES := \
     dict_toolkit_main.cpp
 
-LATIN_IME_DICT_TOOLKIT_SRC_FILES :=
+LATIN_IME_DICT_TOOLKIT_SRC_FILES := \
+    utils/command_utils.cpp
 
 LATIN_IME_DICT_TOOLKIT_TEST_FILES := \
-    dict_toolkit_defines_test.cpp
+    dict_toolkit_defines_test.cpp \
+    utils/command_utils_test.cpp
diff --git a/native/dicttoolkit/UnitTests.mk b/native/dicttoolkit/UnitTests.mk
index d568db4..96e2873 100644
--- a/native/dicttoolkit/UnitTests.mk
+++ b/native/dicttoolkit/UnitTests.mk
@@ -46,6 +46,7 @@
 include $(CLEAR_VARS)
 
 # TODO: Remove -std=c++11 once it is set by default on host build.
+LOCAL_ADDRESS_SANITIZER := true
 LOCAL_CFLAGS += -std=c++11 -Wno-unused-parameter -Wno-unused-function
 LOCAL_CLANG := true
 LOCAL_CXX_STL := libc++
diff --git a/native/dicttoolkit/dict_toolkit_main.cpp b/native/dicttoolkit/dict_toolkit_main.cpp
index d71b50e..22db3d4 100644
--- a/native/dicttoolkit/dict_toolkit_main.cpp
+++ b/native/dicttoolkit/dict_toolkit_main.cpp
@@ -16,8 +16,25 @@
 
 #include <cstdio>
 
+#include "dict_toolkit_defines.h"
+#include "utils/command_utils.h"
+
+void usage(int argc, char **argv) {
+    fprintf(stderr, "Usage: %s <command> [arguments]\n", argc > 0 ? argv[0] : "dicttoolkit");
+}
+
 int main(int argc, char **argv) {
+    if (argc < MIN_ARG_COUNT) {
+        usage(argc, argv);
+        return 0;
+    }
+    using namespace latinime::dicttoolkit;
+    const CommandType commandType = CommandUtils::getCommandType(argv[1]);
+    if (commandType == CommandType::Unknown) {
+        CommandUtils::printCommandUnknownMessage(argv[0], argv[1]);
+        return 0;
+    }
     // TODO: Implement.
-    printf("%s\n", argv[0]);
+    fprintf(stderr, "Command '%s' has not been implemented yet.\n", argv[1]);
     return 0;
 }
diff --git a/native/dicttoolkit/src/dict_toolkit_defines.h b/native/dicttoolkit/src/dict_toolkit_defines.h
index 2a2104e..dbaae0c 100644
--- a/native/dicttoolkit/src/dict_toolkit_defines.h
+++ b/native/dicttoolkit/src/dict_toolkit_defines.h
@@ -19,4 +19,6 @@
 
 #include "defines.h"
 
+#define MIN_ARG_COUNT 2
+
 #endif // LATINIME_DICT_TOOLKIT_DEFINES_H
diff --git a/native/dicttoolkit/src/utils/command_utils.cpp b/native/dicttoolkit/src/utils/command_utils.cpp
new file mode 100644
index 0000000..14fd477
--- /dev/null
+++ b/native/dicttoolkit/src/utils/command_utils.cpp
@@ -0,0 +1,45 @@
+/*
+ * Copyright (C) 2014 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "utils/command_utils.h"
+
+namespace latinime {
+namespace dicttoolkit {
+
+const char *const CommandUtils::COMMAND_NAME_INFO = "info";
+const char *const CommandUtils::COMMAND_NAME_DIFF = "diff";
+const char *const CommandUtils::COMMAND_NAME_MAKEDICT = "makedict";
+const char *const CommandUtils::COMMAND_NAME_HEADER = "header";
+const char *const CommandUtils::COMMAND_NAME_HELP = "help";
+
+/* static */ CommandType CommandUtils::getCommandType(const std::string &commandName) {
+    if (commandName == COMMAND_NAME_INFO) {
+        return CommandType::Info;
+    } else if (commandName == COMMAND_NAME_DIFF) {
+        return CommandType::Diff;
+    } else if (commandName == COMMAND_NAME_MAKEDICT) {
+        return CommandType::Makedict;
+    } else if (commandName == COMMAND_NAME_HEADER) {
+        return CommandType::Header;
+    } else if (commandName == COMMAND_NAME_HELP) {
+        return CommandType::Help;
+    } else {
+        return CommandType::Unknown;
+    }
+}
+
+} // namespace dicttoolkit
+} // namespace latinime
diff --git a/native/dicttoolkit/src/utils/command_utils.h b/native/dicttoolkit/src/utils/command_utils.h
new file mode 100644
index 0000000..7df0dd9
--- /dev/null
+++ b/native/dicttoolkit/src/utils/command_utils.h
@@ -0,0 +1,58 @@
+/*
+ * Copyright (C) 2014 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef LATINIME_DICT_TOOLKIT_COMMAND_UTILS_H
+#define LATINIME_DICT_TOOLKIT_COMMAND_UTILS_H
+
+#include <cstdio>
+#include <string>
+
+#include "dict_toolkit_defines.h"
+
+namespace latinime {
+namespace dicttoolkit {
+
+enum class CommandType : int {
+    Info,
+    Diff,
+    Makedict,
+    Header,
+    Help,
+    Unknown
+};
+
+class CommandUtils {
+public:
+    static CommandType getCommandType(const std::string &commandName);
+
+    static void printCommandUnknownMessage(const std::string &programName,
+            const std::string &commandName) {
+        fprintf(stderr, "Command '%s' is unknown. Try '%s %s' for more information.\n",
+                commandName.c_str(), programName.c_str(), COMMAND_NAME_HELP);
+    }
+
+private:
+    DISALLOW_IMPLICIT_CONSTRUCTORS(CommandUtils);
+
+    static const char *const COMMAND_NAME_INFO;
+    static const char *const COMMAND_NAME_DIFF;
+    static const char *const COMMAND_NAME_MAKEDICT;
+    static const char *const COMMAND_NAME_HEADER;
+    static const char *const COMMAND_NAME_HELP;
+};
+} // namespace dicttoolkit
+} // namespace latinime
+#endif // LATINIME_DICT_TOOLKIT_COMMAND_UTILS_H
diff --git a/native/dicttoolkit/tests/utils/command_utils_test.cpp b/native/dicttoolkit/tests/utils/command_utils_test.cpp
new file mode 100644
index 0000000..9d79c9d
--- /dev/null
+++ b/native/dicttoolkit/tests/utils/command_utils_test.cpp
@@ -0,0 +1,37 @@
+/*
+ * Copyright (C) 2014 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "utils/command_utils.h"
+
+#include <gtest/gtest.h>
+
+namespace latinime {
+namespace dicttoolkit {
+namespace {
+
+TEST(CommandUtilsTests, TestGetCommandType) {
+    EXPECT_EQ(CommandUtils::getCommandType(""), CommandType::Unknown);
+    EXPECT_EQ(CommandUtils::getCommandType("abc"), CommandType::Unknown);
+    EXPECT_EQ(CommandUtils::getCommandType("info"), CommandType::Info);
+    EXPECT_EQ(CommandUtils::getCommandType("diff"), CommandType::Diff);
+    EXPECT_EQ(CommandUtils::getCommandType("makedict"), CommandType::Makedict);
+    EXPECT_EQ(CommandUtils::getCommandType("header"), CommandType::Header);
+    EXPECT_EQ(CommandUtils::getCommandType("help"), CommandType::Help);
+}
+
+} // namespace
+} // namespace dicttoolkit
+} // namespace latinime