Mql4 Guide: How to Create, Clean, and Delete Folders for Your EA

To achieve this in MQL4, you need to utilize the file system functions provided by the API. Note that for security reasons, MQL4 operates within a "sandbox." All file operations (creation, deletion, reading) are restricted to the terminal_data_folder\MQL4\Files directory.

Below is a complete script that performs the following actions:

1. Creates a new folder (or verifies if it already exists).
2. Scans that folder for specific file types (e.g., .log or .txt).
3. Checks the age of each file.
4. Deletes files that are older than a specified number of days.

MQL4 Script: Create Folder and Clean Logs

Save this code as a Script (e.g., CleanLogs.mq4) in your MQL4/Scripts folder.

//+------------------------------------------------------------------+
//|                                                    CleanLogs.mq4 |
//|                        Copyright 2023, MetaQuotes Software Corp. |
//|                                             https://www.mql5.com |
//+------------------------------------------------------------------+
#property copyright "Copyright 2023, MetaQuotes Software Corp."
#property link      "https://www.mql5.com"
#property version   "1.00"
#property strict
#property script_show_inputs

//--- Input Parameters
input string InpFolderName = "MyLogArchives"; // Name of the folder to create/clean
input string InpExtension  = "log";           // File extension to target (e.g., log, txt, csv)
input int    InpDaysOld    = 30;              // Delete files older than this many days

//+------------------------------------------------------------------+
//| Script program start function                                    |
//+------------------------------------------------------------------+
void OnStart()
{
   // 1. Attempt to create the folder
   // Note: This creates the folder inside MQL4\Files\
   if(!FolderCreate(InpFolderName))
   {
      int err = GetLastError();
      // Error 4119 means the folder already exists, which is fine for our purpose
      if(err != 4119) 
      {
         Print("Error creating folder '", InpFolderName, "'. Error Code: ", err);
         return;
      }
      else
      {
         Print("Folder '", InpFolderName, "' already exists. Proceeding to cleanup.");
      }
   }
   else
   {
      Print("Folder '", InpFolderName, "' created successfully.");
   }

   // 2. Define the search filter (e.g., MyLogArchives\*.log)
   string search_path = InpFolderName + "\\*." + InpExtension;
   string file_name;
   
   // 3. Start searching for files in the folder
   // 0 indicates searching in the local MQL4\Files folder
   long search_handle = FileFindFirst(search_path, file_name, 0);

   if(search_handle != INVALID_HANDLE)
   {
      int deleted_count = 0;
      
      do
      {
         // Construct the full path for the file operations
         string full_file_path = InpFolderName + "\\" + file_name;

         // 4. Check if it is a file and not a directory
         if(!FileIsExist(full_file_path)) continue; // Safety check
         
         // Get the file creation date
         long create_date = FileGetInteger(full_file_path, FILE_CREATE_DATE, false);
         
         // Calculate the age of the file in seconds
         long file_age_seconds = TimeCurrent() - create_date;
         long threshold_seconds = InpDaysOld * 24 * 60 * 60;

         // 5. Delete if older than threshold
         if(file_age_seconds > threshold_seconds)
         {
            ResetLastError();
            if(FileDelete(full_file_path))
            {
               Print("Deleted old file: ", file_name, " (Age: ", file_age_seconds/86400, " days)");
               deleted_count++;
            }
            else
            {
               Print("Failed to delete: ", file_name, ". Error: ", GetLastError());
            }
         }
      }
      while(FileFindNext(search_handle, file_name)); // Find the next file

      // 6. Always close the search handle
      FileFindClose(search_handle);
      
      Print("Cleanup complete. Total files deleted: ", deleted_count);
   }
   else
   {
      Print("No files found in '", InpFolderName, "' matching extension *.", InpExtension);
   }
}
//+------------------------------------------------------------------+

Key Functions Explained

1. FolderCreate(string folder_name):

   • Creates a directory in MQL4\Files.
   • If the folder already exists, it returns false and GetLastError() returns 4119. The script handles this gracefully so it can proceed to clean an existing folder.

2. FileFindFirst / FileFindNext / FileFindClose:

   • These are the standard iteration functions.
   • FileFindFirst initializes the search based on a filter (e.g., Folder\*.log).
   • FileFindNext moves to the next file in the list.
   • FileFindClose releases the memory handle used for searching. This is mandatory to prevent memory leaks.

3. FileGetInteger(..., FILE_CREATE_DATE):

   • Retrieves the timestamp of when the file was created.
   • We compare this against TimeCurrent() (the current server time) to determine the file's age.

4. FileDelete(string file_name):

   • Permanently removes the file from the directory.

How to Test

1. Compile the code in MetaEditor.
2. Open your MT4 Data Folder (File -> Open Data Folder).
3. Navigate to MQL4\Files.
4. Manually create a folder named MyLogArchives and put some dummy .log files in it.
5. Drag the script onto a chart in MT4.
6. Check the "Experts" tab in the Terminal window to see the logs of created folders and deleted files.

Q&A

Q: Can I delete files outside the MQL4\Files folder?
A: No. MQL4 runs in a sandbox environment. You cannot access C:\Windows or Desktop directly using standard MQL4 functions. You would need to use a DLL (Windows API) to access files outside the sandbox.

Q: What happens if InpDaysOld is set to 0?
A: The script will delete all files matching the extension in that folder, as every file will be considered "older" than 0 seconds (assuming they weren't created at the exact same millisecond the script ran).

Q: Does FolderCreate support subdirectories?
A: Yes. If you set InpFolderName to "Logs\\StrategyA", it will create the Logs folder and the StrategyA subfolder inside it.