diff --git a/include/os/osString.h b/include/os/osString.h
index 026cb33ad9..5f65f97bec 100644
--- a/include/os/osString.h
+++ b/include/os/osString.h
@@ -37,6 +37,7 @@ typedef int32_t TdUcs4;
     #define wcstombs WCSTOMBS_FUNC_TAOS_FORBID
     #define wcsncpy WCSNCPY_FUNC_TAOS_FORBID
     #define wchar_t WCHAR_T_TYPE_TAOS_FORBID
+    #define strcasestr STR_CASE_STR_FORBID
 #endif
 
 #ifdef WINDOWS
@@ -69,6 +70,8 @@ int32_t taosMbsToWchars(TdWchar *pWchars, const char *pStrs, int32_t size);
 int32_t taosWcharToMb(char *pStr, TdWchar wchar);
 int32_t taosWcharsToMbs(char *pStrs, TdWchar *pWchars, int32_t size);
 
+char *taosStrCaseStr(const char *str, const char *pattern);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/source/os/src/osString.c b/source/os/src/osString.c
index 375c5001f4..7dbd301913 100644
--- a/source/os/src/osString.c
+++ b/source/os/src/osString.c
@@ -236,3 +236,22 @@ int32_t taosMbsToWchars(TdWchar *pWchars, const char *pStrs, int32_t size) { ret
 int32_t taosWcharToMb(char *pStr, TdWchar wchar) { return wctomb(pStr, wchar); }
 
 int32_t taosWcharsToMbs(char *pStrs, TdWchar *pWchars, int32_t size) { return wcstombs(pStrs, pWchars, size); }
+
+char *taosStrCaseStr(const char *str, const char *pattern) {
+  size_t i; 
+
+  if (!*pattern) 
+    return (char*)str; 
+
+  for (; *str; str++) { 
+    if (toupper(*str) == toupper(*pattern)) { 
+    for (i = 1;; i++) { 
+      if (!pattern[i]) 
+      return (char*)str; 
+      if (toupper(str[i]) != toupper(pattern[i])) 
+      break; 
+    } 
+    } 
+  } 
+  return NULL; 
+}
\ No newline at end of file
diff --git a/tools/shell/src/shellEngine.c b/tools/shell/src/shellEngine.c
index 1e832c0c46..39b97004ff 100644
--- a/tools/shell/src/shellEngine.c
+++ b/tools/shell/src/shellEngine.c
@@ -509,7 +509,7 @@ void shellPrintField(const char *val, TAOS_FIELD *field, int32_t width, int32_t
 
 bool shellIsLimitQuery(const char *sql) {
   //todo refactor
-  if (strcasestr(sql, " limit ") != NULL) {
+  if (taosStrCaseStr(sql, " limit ") != NULL) {
     return true;
   }