Tip 207: Retrieving the Short (MS-DOS) Filename from a Long Filename in Windows 95
February 28, 1996
Abstract
Under the Microsoft® Windows® 95 operating system, you can assign a long filename to a file instead of being limited to an 8.3 format. This article explains how to retrieve the short (MS-DOS®) filename assigned to a long filename from within a Microsoft Visual Basic® version 4.0 application.
Short and Long Filenames
When you save a file to disk in MS-DOS® or the Microsoft® Windows® 3.x operating system, you need to specify the filename in an 8.3 format (that is, the name of the file is limited to an eight-character name followed by a period and a three-character filename extension). However, the Microsoft Windows 95 operating system lets you assign a long filename to any file or directory you create.
A long filename can be up to 255 characters in length and can contain individual words describing the file you are creating. For example, a word-processing document might be assigned a long filename (for example, Chapter 1: Working with Long Filenames).
In a Microsoft Visual Basic® version 4.0 application, you may need to manipulate a file by its short (MS-DOS) filename. The example program below provides one method of retrieving the short filename when you know the file's long filename.
Example Program
This program shows how to retrieve the short (MS-DOS) filename assigned to a long filename.
Create a new project in Visual Basic. Form1 is created by default.
Add a Command Button control to Form1. Command1 is created by default.
Add the following code to the Click event for Command1:
Private Sub Command1_Click()
Dim ShortName As String
Dim LongName As String
Dim I As Integer
For I = 0 To File1.ListCount - 1
If File1.Selected(I) = True Then
LongName = "c:\" & File1.List(I)
End If
Next I
ShortName = GetShortNameFromLongName(LongName)
Text1.Text = LongName
Text2.Text = ShortName
End Sub
Add a File List Box control to Form1. File1 is created by default.
Add a Text Box control to Form1. Text1 is created by default.
Add a second Text Box control to Form1. Text2 is created by default.
Create a new function called GetShortNameFromLongName. Add the following code to this function:
Function GetShortNameFromLongName(strLFN As String) As String
On Error GoTo Err_GetShortNameFromLongName
Dim strWork As String
Dim strSFNWork As String
Dim strConvertedFN As String
Dim strPathPart As String
Dim strChar As String
Dim strPathWork As String
Dim I As Integer
Dim intFirstSlash As Integer
Dim fWork As Boolean
intFirstSlash = InStr(strLFN, "\")
If intFirstSlash = 0 Then
GetShortNameFromLongName = ""
Exit Function
End If
strWork = Left(strLFN, intFirstSlash)
I = intFirstSlash + 1
fWork = True
Do While fWork
If I > Len(strLFN) Then
fWork = False
Else
strPathPart = sfnGetToken(Mid(strLFN, I), "\")
strSFNWork = strWork & strPathPart
strConvertedFN = GetShortNameSection(strSFNWork)
If Len(strConvertedFN) = 0 Then
GetShortNameFromLongName = ""
Exit Function
Else
strWork = strWork & strConvertedFN & "\"
End If
I = I + Len(strPathPart) + 1
End If
Loop
GetShortNameFromLongName = Left(strWork, Len(strWork) - 1)
Exit_GetShortNameFromLongName:
Exit Function
Err_GetShortNameFromLongName:
MsgBox "Error: " & Err & ", " & Error$, , "GetShortNameFromLongName_Err"
Resume Exit_GetShortNameFromLongName
End Function
Create a new function called GetShortNameSection. Add the following code to this function (note that each line of code must be typed as a single line of text):
Private Function GetShortNameSection(strLFN As String) As String
On Error GoTo Err_GetShortNameSection
Const INVALID_HANDLE_VALUE = -1
Dim lngRet As Long
Dim intNullPos As Integer
Dim WFD As WIN32_FIND_DATA
lngRet = FindFirstFile(strLFN, WFD)
If lngRet = INVALID_HANDLE_VALUE Then
GetShortNameSection = ""
Else
intNullPos = InStr(WFD.cAlternate, vbNullChar)
If intNullPos <> 1 Then
GetShortNameSection = Left(WFD.cAlternate, intNullPos - 1)
Else
GetShortNameSection = Left(WFD.cFileName, InStr(WFD.cFileName,
vbNullChar) - 1)
End If
End If
Exit_GetShortNameSection:
Exit Function
Err_GetShortNameSection:
MsgBox "Error: " & Err & ", " & Error$, , "GetShortNameSection_Err"
Resume Exit_GetShortNameSection
End Function
Create a new function called sfnGetToken. Add the following code to this function (note that the Private line must be typed as a single line of code):
Private Function sfnGetToken(strTest As String, strDelimiter As String)
As String
Dim intPos As Integer
intPos = InStr(strTest, strDelimiter)
If intPos = 0 Then
sfnGetToken = strTest
Else
sfnGetToken = Left(strTest, intPos - 1)
End If
End Function
Run the example program by pressing Select a long filename from the File List Box control. Click the Command Button control. The long filename appears in the first Text Box control, and the short (MS-DOS) filename is displayed in the second Text Box control.
|