powershell – extract file name and extension

If the file is coming off the disk and as others have stated, use the BaseName and Extension properties:

PS C:\> dir *.xlsx | select BaseName,Extension

BaseName                                Extension
--------                                ---------
StackOverflow.com Test Config           .xlsx  

If you are given the file name as part of string (say coming from a text file), I would use the GetFileNameWithoutExtension and GetExtension static methods from the System.IO.Path class:

PS C:\> [System.IO.Path]::GetFileNameWithoutExtension("Test Config.xlsx")
Test Config
PS H:\> [System.IO.Path]::GetExtension("Test Config.xlsx")
.xlsx