ver since Visual Basic was first released, most of its major features have been overhauled at least once. The exception to this rule is in file operations. Just as in the original basic language, files are still opened using numbers. You can pass the numbers around through your code, but you always have to use somewhat obscure statements to write data to files.
With the release of Visual Basic Scripting Edition, version 2.0, Microsoft introduced the FileSystemObject. This is the overhaul that developers who work with disk files have been waiting for. This object, and other objects in this group, encapsulate all the file operations that previously have been difficult or impossible to implement.
To use these objects, you must reference the Microsoft Scripting Runtime (C:\Windows\System\SCRRUN.DLL) in your Visual Basic application. If you're using VBScript with Internet Explorer, the objects are available already. The objects of interest are these:
Drive. Represents a single storage device, including floppy disk, hard drive, CD-ROM, and more.
Drives. A collection of all the drives in the system.
File. Represents a single disk file somewhere on the system.
Files. A collection of disk files, typically located in a particular directory.
FileSystemObject. An object to represent the entire file system on your computer, including all drives, directories, and files.
Folder. Represents a single directory, whether local or network.
Folders. A collection of directories, which can be located at either the root level or in another directory.
TextStream. Represents a file that has been opened for reading or writing of data.
To get information on all the drives on your system, you could use the following code:
Dim objFSO As New Scripting.FileSystemObject
Dim drvLoop As Scripting.Drive
For Each drvLoop In objFSO.Drives
Debug.Print drvLoop.DriveLetter & ":\"
If drvLoop.DriveType = Fixed _
Or drvLoop.IsReady Then
Debug.Print " Total size: " & Format$(drvLoop.TotalSize / (1024 ^ 2), "#0.00 Mb")
Debug.Print " Free space: " & Format$(drvLoop.FreeSpace / (1024 ^ 2), "#0.00 Mb")
Debug.Print " Volume Label: " & drvLoop.VolumeName
Debug.Print " Disk information unavailable"
Set objFSO = Nothing
Be careful when attempting to access removable drives, especially if you are on a laptop with a swappable drive. Windows still thinks the drive is there in some cases. This can cause some ugly lockups of Visual Basic if you're not careful.
More properties are available for the Drive objectuse the Object Browser to see all the available properties. You can also see online documentation at the Microsoft scripting technologies site.
Besides looping through drives, you can also loop through files in folders. This is especially helpful when you need to search your entire drive for a particular file. Recursion is also helpful in these cases, since you need to keep performing the same action as you work your way down the tree. The following code will count the number of files that have the .GIF extension. This code can obviously be adapted to list the files, do something to each file, and so on. The main point is the actual traversal of the directory tree.
Dim m_lngFileCount As Long
Dim m_objFSO As Scripting.FileSystemObject
Set m_objFSO = New Scripting.FileSystemObject
m_lngFileCount = 0
Debug.Print "Total files: " & m_lngFileCount
Sub CheckFolder(strPath As String)
Dim objFolder As Scripting.Folder
Dim objFile As Scripting.File
Dim objSubdirs As Scripting.Folders
Dim objLoopFolder As Scripting.Folder
Debug.Print "Checking directory " & strPath
Set objFolder = m_objFSO.GetFolder(strPath)
' Check files in this directory
For Each objFile In objFolder.Files
If UCase$(Right$(objFile.ShortPath, 4)) = ".GIF" Then
m_lngFileCount = m_lngFileCount + 1
' Loop through all subdirectories and
' do the same thing.
Set objSubdirs = objFolder.SubFolders
For Each objLoopFolder In objSubdirs
Set objSubdirs = Nothing
Set objFolder = Nothing
To simplify the code, the FileSystemObject and the file counter are made global to this module (hence the m_ prefix). The CheckFolder routine is first called with C:\ as the starting point. This routine first goes through all the files in the selected directory. If any of them match, the counter is incremented. After all the files have been checked, each subdirectory is fed into the CheckFolder routine. This is the recursive part of the codea routine is calling itself. Eventually, there are no more subdirectories and all the CheckFolder calls end. The total is then printed by Sub Main.
If you ever built this code using the Dir function, you should appreciate the simplicity of this version. No longer do you have to check file attributes or try to keep track of where you are at in the recursion. The new file objects take care of the dirty work for you.