diff --git a/fileop.cpp b/fileop.cpp
index 977ce98..10ec138 100644
--- a/fileop.cpp
+++ b/fileop.cpp
@@ -1,4 +1,4 @@
-#if HAVE_UTILS_CONFIG_H
+#if HAVE_UTILS_CONFIG_H
 #include "utils_config.h"
 #endif
 
@@ -700,3 +700,11 @@ FILE* fileop::fopen(std::string path, std::string mode) {
     return ::fopen(path.c_str(), mode.c_str());
 #endif
 }
+
+std::string fileop::extname(std::string path) {
+    auto loc = path.find_last_of('.');
+    if (loc == std::string::npos) {
+        return "";
+    }
+    return path.substr(loc + 1, path.length() - loc - 1);
+}
diff --git a/fileop.h b/fileop.h
index 35f3743..7f814f0 100644
--- a/fileop.h
+++ b/fileop.h
@@ -1,4 +1,4 @@
-#ifndef _UTIL_FILEOP_H
+#ifndef _UTIL_FILEOP_H
 #define _UTIL_FILEOP_H
 #include <list>
 #include <string>
@@ -199,5 +199,11 @@ namespace fileop {
      */
     std::string relpath(std::string path, std::string start = "");
     FILE* fopen(std::string path, std::string mode);
+    /**
+     * @brief Get file extension name
+     * @param path Path
+     * @return File extension name. If no extension, will return empty string.
+    */
+    std::string extname(std::string path);
 }
 #endif