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Published: Tuesday, October 31, 2000

Picking Out Delimited Text with Regular Expressions, Part 2


  • Read Part 1

  • In Part 1 we looked at the difference between greedy and non-greedy repetition matching with regular expressions. We also started a coding example. In this part we'll finish out our coding example, look at another coding example, and wrap the article up!

    - continued -

    '

    'Create a regular expression object
    Dim objRegExp
    Set objRegExp = New RegExp
    
    'Set our pattern
    objRegExp.Pattern = "<title>(.*?)<\/title>"
    objRegExp.IgnoreCase = True
    objRegExp.Global = True
    
    'Get the matches from the contents of our HTML file, strContents
    Dim objMatches
    Set objMatches = objRegExp.Execute(strContents)
    

    At this point we have all of our regular expression "matches" stored in a collection, objMatches. Since objMatches is just an ordinary collection, we can do a number of things at this point: we can iterate through the collection with a For Each ... Next, we can access a particular match randomly, etc. If the HTML document lacked a title, the objMatches.Count property will return zero. Else, we have found a title and want to display it. Keep in mind that the regular expression engine will return the both the delimiters and the text between them. So, if /SomePage.htm contained a title tag like: <TITLE>Hello, World!</TITLE>, the resulting match would be exactly that... not just "Hello, World!" For that reason, before displaying the title, we need to strip it out. (For that we'll use the Mid function, a standard VBScript string function.)

    If objMatches.Count > 0 then
      Response.Write "The Web page title is: " & _
          Mid(objMatches(0).Value, 8, Len(objMatches(0).Value) - 16)
    Else
      Response.Write "No TITLE tag found."
    End If
    
    Set objRegExp = Nothing     'Clean up!
    
    [Try out the live demo!]

    Another example of using the non-greedy repetition regular expression feature is listing all of the text that appears between bold tags (or italics, or underlined, or whatnot). To accomplish this, we simply need to alter our regular expression:

    'Set our pattern
    objRegExp.Pattern = "<b>(.*?)<\/b>"
    objRegExp.IgnoreCase = True
    objRegExp.Global = True
    
    'Get the matches from the contents of our HTML file, strContents
    Dim objMatches
    Set objMatches = objRegExp.Execute(strContents)
    

    Now, instead of just outputting a specifc match in the objMatches collection, let's list each match:

    Dim objMatch
    For Each objMatch in objMatches
      Response.Write objMatch.Value & "<BR>"
    Next
    
    [View the live demo!]

    I hope this article has proved to be both interesting and educational! Remember, for the non-greedy repetition regular expressions to work, you will need the VBScript Scripting Engine 5.5 or higher. Again, to download the latest version of the VBScript Scripting Engine visit http://msdn.microsoft.com/scripting/; to determine what server-side scripting engine version you're using, be sure to read: Determining the Server-Side Scripting Language and Version!

    Happy Programming!


    Attachments:

  • Visit the Regular Expressions Article Index
  • Read Determining the Server-Side Scripting Language and Version
  • Download the latest VBScript Scripting Engine
  • Visit the Regular Expressions Forum



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