Question

I am trying to create a regular expression to validate file names for further processing.

I want to match a file with extension .txt, .csv, or .log
but I want to exclude them if it ENDS with _out.csv or mylog.log

Here is my start:

    Function CanProcessFile(strFileNameIn, strLogName, strOutName)
      Dim objRegEx, colMatches, strPattern
      Set objRegEx = CreateObject("VBScript.RegExp")
      strPattern = "((.txt$)|(.csv$)|(.Log$))"
      strPattern = "(?!(" & strLogName & "$))" & strPattern
      'strPattern = "(?!(" & strOutName & "$))" & strPattern
      objRegEx.Pattern = strPattern
      objRegEx.IgnoreCase = True
      Set colMatches = objRegEx.Execute(strFileNameIn)
      If colMatches.Count > 0 Then
        CanProcessFile = True
      Else
        CanProcessFile = False
      End If
    End Function

but every time I try to add a ^ or ?! with (_out.csv$) it fails.

Answer 1

I think that creating two filters (as you suggest in a comment above) may well be the best way to go, but if you prefer to do it in a single regex, then you should be able to write:

objRegEx.Pattern = "^(?!.*(_out\.csv|mylog\.log)$).*\.(txt|csv|log)$"

which ensures that the file doesn’t start with .*(_out\.csv|mylog\.log)$ (i.e., that it doesn’t end with _out.csv or mylog.log).