fix bug in linux

@@ -130,7 +130,7 @@ void concate_files(vector<string > merged_files)
 
 	for (int i = 0; i < merged_files.size(); i++) {
 		strcat(buf, " ");
-		strcat(buf, merged_files[0].c_str());
+		strcat(buf, merged_files[i].c_str());
 	}
 	strcat(buf, ">");
 #endif // WIN32