vbs check if file exists

To check if a file exists using Visual Basic Script (VBS) in C++, you can use the FileSystemObject class from the Scripting namespace. The FileSystemObject class provides methods to perform various file system operations, including checking if a file exists.

Here's an example code snippet that demonstrates how to check if a file exists using VBS in C++:

#include <windows.h>
#include <iostream>

int main() {
    // Create an instance of the FileSystemObject
    IDispatch* pFso = NULL;
    HRESULT hr = CoCreateInstance(CLSID_ScriptingFileSystemObject, NULL,
                                  CLSCTX_INPROC_SERVER, IID_IDispatch, (void)&pFso);
    if (SUCCEEDED(hr)) {
        // Convert the file path to a BSTR
        BSTR filePath = SysAllocString(L"C:\\path\\to\\file.txt");

        // Check if the file exists
        VARIANT_BOOL fileExists;
        DISPID dispid;
        OLECHAR* methodName = L"FileExists";
        hr = pFso->GetIDsOfNames(IID_NULL, &methodName, 1, LOCALE_USER_DEFAULT, &dispid);
        if (SUCCEEDED(hr)) {
            DISPPARAMS params = {};
            params.cArgs = 1;
            params.cNamedArgs = 0;
            params.rgvarg = new VARIANT[1];
            VariantInit(&params.rgvarg[0]);
            params.rgvarg[0].vt = VT_BSTR;
            params.rgvarg[0].bstrVal = filePath;

            EXCEPINFO excepInfo = {};
            UINT argErr = 0;
            hr = pFso->Invoke(dispid, IID_NULL, LOCALE_USER_DEFAULT, DISPATCH_METHOD,
                              &params, NULL, &excepInfo, &argErr);
            if (SUCCEEDED(hr)) {
                fileExists = params.rgvarg[0].boolVal;
                VariantClear(&params.rgvarg[0]);
            }

            delete[] params.rgvarg;
        }

        // Display the result
        if (fileExists) {
            std::cout << "File exists" << std::endl;
        } else {
            std::cout << "File does not exist" << std::endl;
        }

        // Clean up
        SysFreeString(filePath);
        pFso->Release();
    }

    return 0;
}

Let's break down the code and explain each step:

Include the necessary headers: windows.h for Windows APIs and iostream for standard input/output operations.
Define the main function as the entry point of the program.
Create an instance of the IDispatch interface, which represents an automation object in COM (Component Object Model).
Use the CoCreateInstance function to create an instance of the FileSystemObject class. The CLSID_ScriptingFileSystemObject is the class identifier for the FileSystemObject.
Check if the creation of the FileSystemObject instance succeeded by checking the return value of CoCreateInstance.
Allocate a BSTR (Basic String) to store the file path. The file path should be specified as a wide character string (L"...").
Check if the file exists using the FileExists method of the FileSystemObject. To do this, you need to get the method ID (dispid) of FileExists using the GetIDsOfNames method.
Set up the input parameters for the FileExists method. In this case, there is only one parameter - the file path, which is passed as a BSTR in the rgvarg array.
Invoke the FileExists method using the Invoke method of the IDispatch interface. This will execute the method and return the result.
Check if the invocation of the FileExists method succeeded by checking the return value of Invoke.
Retrieve the result of the FileExists method from the VARIANT in the rgvarg array.
Clear the VARIANT to release any resources it may hold.
Display the result based on whether the file exists or not.
Clean up allocated resources, such as the BSTR and the IDispatch interface.
Return 0 to indicate successful execution of the program.

This code demonstrates how to check if a file exists using VBS in C++. It uses the FileSystemObject class from the Scripting namespace to perform the file existence check.