[RESOLVED] Finding the relative path of file

[eyeRmonkey]

I am starting a new thread on this because the last one I posted turned into a debate between randem and I.

I was wondering if anyone knew of a class module/DLL out there that finds the relative path of a file in a reliable manner. For example, I would pass these strings to a method:

"C:\Projects\My Project 1\Forms\MyForm.frm" <--- Path to make relative
"C:\Projects\My Project 1\" <--- Path to use as absolute
... should return ...
"\Forms\MyForm.frm"

Here is another example:
"C:\Common\By wossy\sandpaper.dll" <--- Path to make relative
"C:\Projects\My Project 1\" <--- Path to use as absolute
... should return ...
"..\..\Common\By wossy\sandpaper.dll"

There should also be another sub to unfold the relative paths. For example:
"D:\Another Guy\Coding Stuff\Project 132\" <--- Path to use as absolute
"\Forms\MyForm.frm"<--- Relative Path
... should return ...
"D:\Another Guy\Coding Stuff\Project 132\Forms\MyFrom.frm"

Does anyone know of a way to do this reliably? I have a feeling that if I wrote my own code to do it I would miss a few big things. This has to have been done before.

[Dave Sell]

You might use the Right() and Len() function to kind of subtract the Absolute path from the path in question...

[Harsh Gupta]

probably u can use Split() by "\" and then append or delete the required part of the path!!!!

[eyeRmonkey]

I guess I will just write it then. I think I will split() it on "\" (after replacing any "/" with "\") and then loop through and compare and take action when necessary.

[dglienna]

Instr() will let you know if you have a folder or not. Don't use anything else first.

[eyeRmonkey]

What do you mean don't use anything else first?

[eyeRmonkey]

Okay here is what I came up with. Could you guys help me work out the bugs? I don't see any problems with it, but there must be some:

'---------------------------------------------------------------------------------------
' Module    : modRelativePaths
' DateTime  : 10/16/2005 02:19
' Author    : Jeremy Blanchard
' Purpose   :
'---------------------------------------------------------------------------------------
 
Option Explicit
 
'---------------------------------------------------------------------------------------
' Procedure : MakePathRelative
' DateTime  : 10/16/2005 02:19
' Author    : Jeremy Blanchard
' Purpose   : Make sure to include either a \ at the end or a \filename.txt at the end
'    of the paths
'---------------------------------------------------------------------------------------
'
Public Function MakePathRelative( _
        ByVal sToMakeRelative As String, _
        ByVal sAbsolutePath As String) As String
    Dim i       As Long
    Dim j       As Long
    Dim sRel()  As String
    Dim sAbs()  As String
    Dim sReturn As String
    
    sToMakeRelative = Replace$(sToMakeRelative, "/", "\", , , vbTextCompare)
    sAbsolutePath = Replace$(sAbsolutePath, "/", "\", , , vbTextCompare)
    
    sRel = Split(sToMakeRelative, "\", , vbTextCompare)
    sAbs = Split(sAbsolutePath, "\", , vbTextCompare)
    
    For i = 0 To UBound(sAbs) - 1
        If sRel(i) = sAbs(i) Then
            ' Do nothing but increment i
        Else
            For j = i To UBound(sAbs) - 1
                sReturn = sReturn & "..\"
            Next j
            Exit For
        End If
    Next i
    
    For i = i To UBound(sRel)
        sReturn = sReturn & sRel(i)
        If i <> UBound(sRel) Then _
            sReturn = sReturn & "\"
    Next i
    
    MakePathRelative = sReturn
    
End Function
 
 
'---------------------------------------------------------------------------------------
' Procedure : MakePathAbsolute
' DateTime  : 10/16/2005 02:19
' Author    : Jeremy Blanchard
' Purpose   : Make sure to include either a \ at the end or a \filename.txt at the end
'    of the paths
'---------------------------------------------------------------------------------------
'
Public Function MakePathAbsolute( _
        ByVal sRelativePath As String, _
        ByVal sAbsolutePath As String) As String
    Dim i           As Long
    Dim j           As Long
    Dim sRel()      As String
    Dim sAbs()      As String
    Dim sReturn     As String
    Dim sPartial    As String
    
    sRelativePath = Replace$(sRelativePath, "/", "\", , , vbTextCompare)
    sAbsolutePath = Replace$(sAbsolutePath, "/", "\", , , vbTextCompare)
    
    sRel = Split(sRelativePath, "\", , vbTextCompare)
    sAbs = Split(sAbsolutePath, "\", , vbTextCompare)
    
    For i = 0 To UBound(sRel) - 1
        If sRel(i) = ".." Then
            ' Do nothing but increment i
        Else
            For j = i To UBound(sRel)
                sReturn = sReturn & sRel(j)
                If j <> UBound(sRel) Then _
                    sReturn = sReturn & "\"
            Next j
            Exit For
        End If
    Next i
    
    For i = 0 To UBound(sAbs) - 1 - i
        sPartial = sPartial & sAbs(i)
        If i <> UBound(sAbs) - i Then _
            sPartial = sPartial & "\"
    Next i
    sReturn = sPartial & sReturn
    
    MakePathAbsolute = sReturn
End Function

Attached is the sample project.

[Joacim Andersson]

I haven't tested your code, but don't you think it would be safer to use the correct API functions instead?

Private Declare Function PathRelativePathTo _
 Lib "shlwapi.dll" Alias "PathRelativePathToA" ( _
 ByVal pszPath As String, _
 ByVal pszFrom As String, _
 ByVal dwAttrFrom As Long, _
 ByVal pszTo As String, _
 ByVal dwAttrTo As Long) As Long
 
Private Declare Function PathCombine _
 Lib "shlwapi.dll" Alias "PathCombineA" ( _
 ByVal szDest As String, _
 ByVal lpszDir As String, _
 ByVal lpszFile As String) As Long
 
Public Function MakePathRelative( _
 ByVal sFrom As String, _
 ByVal sTo As String) As String
    Const FILE_ATTRIBUTE_DIRECTORY As Long = &H10
    Const MAX_PATH As Long = 260
    Dim sRet As String
    Dim nFlagFrom As Long, nFlagTo As Long
    
    If Right$(sFrom, 1) = "\" Then
        nFlagFrom = FILE_ATTRIBUTE_DIRECTORY
        sFrom = Left$(sFrom, Len(sFrom) - 1)
    End If
    If Right$(sTo, 1) = "\" Then
        nFlagTo = FILE_ATTRIBUTE_DIRECTORY
        sTo = Left$(sTo, Len(sTo) - 1)
    End If
    sRet = Space$(MAX_PATH)
    If PathRelativePathTo(sRet, sFrom, nFlagFrom, sTo, nFlagTo) Then
        MakePathRelative = Left$(sRet, InStr(sRet, vbNullChar) - 1)
    End If
End Function
 
Public Function MakePathAbs(ByVal sRel As String, ByVal sAbs As String)
    'sAbs must be the path of a directory and NOT a file
    'The relative path can be a relative path to a file
    Const MAX_PATH As Long = 260
    Dim sRet As String
    sRet = Space$(MAX_PATH)
    If PathCombine(sRet, sAbs, sRel) Then
        MakePathAbs = Left$(sRet, InStr(sRet, vbNullChar) - 1)
    End If
End Function

In this case I did as you and in MakePathRelative you must end the path strings with a backslash to indicate a directory, if not it assumes it is the path to a file. In MakePathAbs the absolute path must be to a directory, but it doesn't matter if it has a trailing backslash or not since a directory is assumed. The relative path could be either to a file or a directory.

[eyeRmonkey]

Well now you tell me!

That is what I had been looking for for the last few days when I started 2 threads on this subject. After I finally get my act together and write some code, you show me what I wanted the whole time.

Thanks though! I'll take a look at it later today.

[Joacim Andersson]

Well, I beg your pardon for not monitoring all the threads you start and immediatly reply to them . But the fact is that I didn't see this thread before you sent an e-mail to me about it

[eyeRmonkey]

I was just giving you a bad time.

Thanks a ton for the code though.