diff --git a/backend/src/lexer.cpp b/backend/src/lexer.cpp
index 8fed0b8..c470e02 100644
--- a/backend/src/lexer.cpp
+++ b/backend/src/lexer.cpp
@@ -270,7 +270,7 @@ bool CommandShowLexer(const std::string &command, std::string &ISBN,
 bool CommandBuyLexer(const std::string &command, std::string &ISBN,
                      int &quantity) {
   static std::basic_regex main_pattern(
-      R"(^ *buy +(?:\S{1,20}) +[0-9]{1,10} *$)",
+      R"(^ *buy +(?:[!-~]{1,20}) +[0-9]{1,10} *$)",
       std::regex_constants::optimize);
   if (std::regex_match(command, main_pattern)) {
     std::stringstream ss(command);
@@ -302,7 +302,7 @@ bool CommandBuyLexer(const std::string &command, std::string &ISBN,
 */
 // clang-format on
 bool CommandSelectLexer(const std::string &command, std::string &ISBN) {
-  static std::basic_regex main_pattern(R"(^ *select +(?:\S{1,20}) *$)",
+  static std::basic_regex main_pattern(R"(^ *select +(?:[!-~]{1,20}) *$)",
                                        std::regex_constants::optimize);
   if (std::regex_match(command, main_pattern)) {
     std::stringstream ss(command);
@@ -336,7 +336,7 @@ bool CommandModifyLexer(const std::string &command, std::string &ISBN,
                         std::string &name, std::string &author,
                         std::string &keyword, double &price) {
   static std::basic_regex main_pattern(
-      R"(^ *modify(?: +-ISBN=(?:\S{1,20})| +-name=\"(?:[^\s"]{1,60})\"| +-author=\"(?:[^\s"]{1,60})\"| +-keyword=\"(?:[^\s"]{1,60})\"| +-price=[0-9]{1,10}(?:\.[0-9]+)?)+ *$)",
+      R"(^ *modify(?: +-ISBN=(?:[!-~]{1,20})| +-name=\"(?:[!#-~]{1,60})\"| +-author=\"(?:[!#-~]{1,60})\"| +-keyword=\"(?:[^\s"]{1,60})\"| +-price=[0-9]{1,10}(?:\.[0-9]+)?)+ *$)",
       std::regex_constants::optimize);
   if (std::regex_match(command, main_pattern)) {
     std::stringstream ss(command);