Visual Basic for Applications:
Creating a temporary file

How to:

In VBA, creating a temporary file can be achieved using the FileSystemObject available in the Microsoft Scripting Runtime library. This object provides methods to create, read, write, and delete files and folders. Here’s a step-by-step guide on creating a temporary file:

1. Enable Microsoft Scripting Runtime: First, ensure the Microsoft Scripting Runtime reference is enabled in your VBA environment. Go to Tools > References in the VBA editor, and check “Microsoft Scripting Runtime”.

2. Creating a Temporary File: The following VBA code demonstrates how to create a temporary file in the default temporary folder.

Sub CreateTemporaryFile()
    Dim fso As Object
    Dim tmpFile As Object
    
    ' Create FileSystemObject
    Set fso = CreateObject("Scripting.FileSystemObject")
    
    ' Get path of the temporary folder
    Dim tempFolder As String
    tempFolder = fso.GetSpecialFolder(2) ' 2 indicates the temporary folder
    
    ' Create a temporary file and get a reference to it
    Set tmpFile = fso.CreateTextFile(tempFolder & "\myTempFile.txt", True)
    
    ' Write something to the file
    tmpFile.WriteLine "This is a test."
    
    ' Close the file
    tmpFile.Close
    
    ' Optionally, print the path for reference
    Debug.Print "Temporary file created at: " & tempFolder & "\myTempFile.txt"
End Sub

3. Sample Output: When you run the above code, it creates a temporary file named myTempFile.txt in the temporary folder and writes a line of text to it. If you have the Immediate Window open (Ctrl + G in the VBA editor), you’ll see:

Temporary file created at: C:\Users\[YourUsername]\AppData\Local\Temp\myTempFile.txt

Deep Dive

The method shown uses the FileSystemObject (FSO) part of the Microsoft Scripting Runtime. FSO is a powerful tool for file system manipulation, introduced with Visual Basic Scripting Edition. Despite its age, it remains widely used in VBA for its simplicity and breadth of functionality.

Creating temporary files plays a critical role in many programming and scripting tasks, providing a sandbox for testing or a workspace for processes that don’t require permanent storage. However, developers should handle these files with care, ensuring they are removed or cleared when no longer needed, to prevent accidental data leakage or unnecessary consumption of disk space.

While VBA provides native methods for dealing with files and folders, the FileSystemObject offers a more object-oriented approach, which might be more familiar to programmers coming from other languages. Nevertheless, newer technologies or languages might offer more robust or secure methods for handling temporary files, such as utilizing in-memory data structures or specialized temporary file libraries in environments like Python or .NET. In these cases, although VBA can serve well for quick tasks or integration within Office applications, exploring alternatives for more extensive or security-sensitive applications is advisable.