How do I determine if a path is relative or absolute with VB Scripting Host

Question

How do I determine if a path is relative or absolute in Visual Basic Script.

In VBA, I'd call the Win32 Api function PathIsRelative

Private Declare Function PathIsRelative Lib "shlwapi" _
    Alias "PathIsRelativeA" _
   (ByVal pszPath As String) As Long

However, it's not possible to call into a DLL from VBS, so I cannot use the Win32 Api.

René

Answer 1

set oFSO = CREATEOBJECT("Scripting.FileSystemObject")

relativePath = ""
absolutePath = "c:\test"

MsgBox UCase(relativePath) = UCase(oFSO.GetAbsolutePathName(relativePath))
MsgBox UCase(absolutePath) = UCase(oFSO.GetAbsolutePathName(absolutePath))

Answer 2

Late, but according to Microsoft Naming Files, Paths, and Namespaces page referenced by a Helen's comment, a path is absolute if:

• a UNC name of any format, which always start with two backslash characters ("\\").
• A disk designator with a backslash, for example "C:\" or "d:\".
• A single backslash, for example, "\directory" or "\file.txt".

Otherwise, according to the page, the path is relative.

At most the first three characters are to be checked here (checking if the path is valid, i.e. whose items don't contain illegal characters or aren't a reserved name like CON) seems out of the scope.

Here's my two cents:

Function isAbsolutePath(path)
    isAbsolutePath = True
    Dim first : first = UCase(Left(path, 1))
    Dim secondNthird : secondNthird = UCase(Mid(path, 2, 2))
    If first > "A" and first < "Z" and secondNthird = ":\" Then Exit Function
    If first = "\" Then Exit Function
    isAbsolutePath = False
End Function

Test code:

Function IIf(clause, thenValue, elseValue)
    If CBool(clause) Then
        IIf = thenValue
    Else 
        IIf = elseValue
    End If
End Function

For Each path in Array ( _
        "C:\Test1", _
        "D:\Test2\", _
        "3:\Test4", _
        "CD:\Test5", _
        "\\Test6\", _
        "\Test7", _
        "Test8", _
        ".\Test9\", _
        "..\Test10" _
    )
    Response.Write path & ": " & IIf(isAbsolutePath(path), "absolute", "relative")  & "</br>"
Next

Output:

C:\Test1: absolute
D:\Test2\: absolute
3:\Test4: relative
CD:\Test5: relative
\\Test6\: absolute
\Test7: absolute
Test8: relative
.\Test9\: relative
..\Test10: relative

Of course, as said, you must ensure next your path is valid (3:\Test4 is relative but illegal).