ACC2000: Sample Function to Generate a Random Temporary File Name

This article shows you how to create a sample function that generates a random file name that can be used for a temporary file.

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Sometimes, an application has to create a file that it uses temporarily and then deletes. The names of temporary files are important and you do not want your application to inadvertently overwrite an existing file.

In such cases, you can create and use the user-defined function called MakeTempFileName(). This function accepts a file extension and returns a string representing a non-existent, random file name with the file extension that you specify. The file name includes a path to your Windows Temp folder (directory) so that the temporary file is placed in the same folder that Windows uses to write its temporary files. This is handy for those who perform periodic maintenance on their hard disks and delete any leftover temporary files in the Windows Temp folder.

To create the sample function MakeTempFileName(), follow these steps:

1. Create a module and type the following line in the Declarations section if it is not already there:

   Option Explicit

2. Type the following procedure:

   Function MakeTempFileName(Extension As String) As String
   
      Dim Isfile As Integer, FHandle As Integer, Cntr As Integer
      Dim WinTemp As String, TF As String
   
      Isfile = False
      FHandle = FreeFile
   
      WinTemp = Environ("TEMP") & "\"
      For Cntr = 1 To 8
         WinTemp = WinTemp & Mid(LTrim(Str(CInt(Rnd * 10))), 1, 1)
      Next Cntr
   
      TF = Trim(WinTemp$) & "." & Extension
   
      Open TF For Output As #Fhandle
      Debug.Print TF
      Print #FHandle, "This is a Temp file"
        
      Close #FHandle
      MakeTempFileName = TF
   
   End Function

3. Type the following line in the Immediate window and press ENTER:

   TempFileName$ = MakeTempFileName("TMP")

   Note that the name of the temporary file is displayed in the Immediate window. The file contains the line "This is a Temp file." After you have verified that the file exists in your Temp folder, you can delete it.