diff --git a/backend/include/bs-utility.h b/backend/include/bs-utility.h
index 6598136..32c7ee0 100644
--- a/backend/include/bs-utility.h
+++ b/backend/include/bs-utility.h
@@ -140,4 +140,21 @@ class OperationLogItemClass {
   char command[256];
   int fid;
 };
+
+enum OperationType {
+  __Ksu,
+  __Klogout,
+  __Kregister,
+  __Kpasswd,
+  __Kuseradd,
+  __Kdelete,
+  __Kshow,
+  __Kbuy,
+  __Kselect,
+  __Kmodify,
+  __Kimport,
+  __Kshowfinance,
+  __Klog,
+  __Kreport,
+};
 #endif  // PROTECTOR_UTILITY_H
\ No newline at end of file
diff --git a/backend/include/engine.h b/backend/include/engine.h
index 3790c92..d9f4f2e 100644
--- a/backend/include/engine.h
+++ b/backend/include/engine.h
@@ -5,13 +5,14 @@
 #include <vector>
 
 #include "database.h"
+#include "lexer.h"
 class BookStoreEngineClass {
   std::string config_dir;
   UserDataBase user_data_base;
-
+  bool is_server;
  public:
   BookStoreEngineClass() = delete;
-  BookStoreEngineClass(std::string __config_dir);
+  BookStoreEngineClass(std::string __config_dir, bool __is_server);
   std::vector<std::string> Execute(const std::string &cmd,
                                    std::stack<std::string> &login_stack);
 };
diff --git a/backend/include/lexer.h b/backend/include/lexer.h
new file mode 100644
index 0000000..81ec949
--- /dev/null
+++ b/backend/include/lexer.h
@@ -0,0 +1,10 @@
+#ifndef PROTECTOR_LEXER_H
+#define PROTECTOR_LEXER_H
+#include <regex>
+#include <sstream>
+#include <string>
+#include <vector>
+bool CommandShowLexer(const std::string &command, std::string &ISBN,
+                      std::string &name, std::string &author,
+                      std::string &keyword);
+#endif  // PROTECTOR_LEXER_H
\ No newline at end of file
diff --git a/backend/src/builtin-cli.cpp b/backend/src/builtin-cli.cpp
index 5ed1d3b..a681f7c 100644
--- a/backend/src/builtin-cli.cpp
+++ b/backend/src/builtin-cli.cpp
@@ -9,7 +9,7 @@
 #include "bs-utility.h"
 #include "engine.h"
 void BookStoreMain(bool is_server, std::string config_dir) {
-  BookStoreEngineClass engine(config_dir);
+  BookStoreEngineClass engine(config_dir, is_server);
   std::ios::sync_with_stdio(false);
   if (!is_server) {
     std::stack<std::string> login_stack;
diff --git a/backend/src/engine.cpp b/backend/src/engine.cpp
index 849db28..8e14942 100644
--- a/backend/src/engine.cpp
+++ b/backend/src/engine.cpp
@@ -2,18 +2,78 @@
 
 #include <stack>
 #include <string>
+#include <unordered_map>
 
 #include "bs-utility.h"
 
-BookStoreEngineClass::BookStoreEngineClass(std::string __config_dir) {
+BookStoreEngineClass::BookStoreEngineClass(std::string __config_dir,
+                                           bool __is_server) {
   config_dir = __config_dir;
   user_data_base.Open(config_dir + "user");
+  is_server = __is_server;
 }
 std::vector<std::string> BookStoreEngineClass::Execute(
     const std::string &cmd, std::stack<std::string> &login_stack) {
-  if (cmd == "quit" || cmd == "exit") {
-    BookStore_ZYM::shut_down = true;
+  static std::unordered_map<std::string, OperationType> operation_map = {
+      {"su", OperationType::__Ksu},
+      {"logout", OperationType::__Klogout},
+      {"useradd", OperationType::__Kuseradd},
+      {"register", OperationType::__Kregister},
+      {"delete", OperationType::__Kdelete},
+      {"passwd", OperationType::__Kpasswd},
+      {"select", OperationType::__Kselect},
+      {"modify", OperationType::__Kmodify},
+      {"import", OperationType::__Kimport},
+      {"show", OperationType::__Kshow},
+      {"buy", OperationType::__Kbuy},
+      {"report", OperationType::__Kreport},
+      {"log", OperationType::__Klog}};
+  std::stringstream ss(cmd);
+  std::string head = "";
+  ss >> head;
+  if (head == "quit" || head == "exit") {
+    if (!is_server) BookStore_ZYM::shut_down = true;
     return std::vector<std::string>();
   }
+  if (operation_map.find(head) == operation_map.end()) {
+    for (int i = 0; i < cmd.length(); i++)
+      if (cmd[i] != ' ') return std::vector<std::string>({"Invalid"});
+    return std::vector<std::string>();
+  }
+  switch (operation_map[head]) {
+    case OperationType::__Ksu: {
+    }
+    case OperationType::__Klogout: {
+    }
+    case OperationType::__Kuseradd: {
+    }
+    case OperationType::__Kregister: {
+    }
+    case OperationType::__Kdelete: {
+    }
+    case OperationType::__Kpasswd: {
+    }
+    case OperationType::__Kselect: {
+    }
+    case OperationType::__Kmodify: {
+    }
+    case OperationType::__Kimport: {
+    }
+    case OperationType::__Kshow: {
+      ss >> head;
+      if (head == "finance") goto dst_showfinance;
+    }
+    case OperationType::__Kshowfinance: {
+    dst_showfinance:;
+    }
+    case OperationType::__Kbuy: {
+    }
+    case OperationType::__Kreport: {
+      throw FatalError("report Not implemented", 2);
+    }
+    case OperationType::__Klog: {
+      throw FatalError("log Not implemented", 3);
+    }
+  }
   return std::vector<std::string>({cmd});
 }
\ No newline at end of file
diff --git a/backend/src/lexer.cpp b/backend/src/lexer.cpp
new file mode 100644
index 0000000..dee0b79
--- /dev/null
+++ b/backend/src/lexer.cpp
@@ -0,0 +1,45 @@
+#include "lexer.h"
+bool CommandShowLexer(const std::string &command, std::string &ISBN,
+                      std::string &name, std::string &author,
+                      std::string &keyword) {
+  static std::basic_regex main_pattern(
+      R"(^ *show(?: +-ISBN=(?:\S{1,20})| +-name=\"(?:[^\s"]{1,60})\"| +-author=\"(?:[^\s"]{1,60})\"| +-keyword=\"(?:[^\s"]{1,60})\")* *$)",
+      std::regex_constants::optimize);
+
+  std::smatch results;
+  bool has_ISBN = false;
+  bool has_name = false;
+  bool has_author = false;
+  bool has_keyword = false;
+  ISBN = "";
+  name = "";
+  author = "";
+  keyword = "";
+  if (std::regex_match(command, results, main_pattern)) {
+    std::stringstream ss(command);
+    std::string token;
+    ss >> token;
+    while (ss >> token) {
+      if (token[1] == 'I') {
+        if (has_ISBN) return false;
+        has_ISBN = true;
+        ISBN = token.substr(6);
+      } else if (token[1] == 'n') {
+        if (has_name) return false;
+        has_name = true;
+        name = token.substr(6 + 1, token.size() - 7 - 1);
+      } else if (token[1] == 'a') {
+        if (has_author) return false;
+        has_author = true;
+        author = token.substr(8 + 1, token.size() - 9 - 1);
+      } else if (token[1] == 'k') {
+        if (has_keyword) return false;
+        has_keyword = true;
+        keyword = token.substr(9 + 1, token.size() - 10 - 1);
+      } else
+        return false;
+    }
+    return true;
+  } else
+    return false;
+}
\ No newline at end of file