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Published: Wednesday, September 01, 1999

An Introduction to Regular Expression with VBScript, Part 2


  • Read Part 1

  • In Part 1 we discussed the "rules" of regular expression. In this article I will show you how to use the regular expression object inherent in VBScript 5. (If you do not have the VBScript 5 Scripting engine installed, refer to Part 1 for installation instructions.)

    - continued -

    First things first: you need to create an instance of the regexp object. This can be accomplished with the following code:

    'Always do this: (good programming practice!) Option Explicit 'Declare our variable Dim objRegExpr 'Create an instance of the regexp object Set objRegExpr = New regexp

    There are a couple of nifty properties in the regexp object. One such property is the Pattern property. We set this property equal to our regular expression. So, let's say that we are wanting to search a string for a valid phone number (a very common regular expression-tutorial question). Let's say that all phone numbers will have this form:

    (XXX)XXX-XXXX

    Note that there are no spaces in that string. So, our regular expression could look like:

    \([0-9]{3}\)[0-9]{3}-[0-9]{4}

    Note: We need the backslashes before the parenthesis because the parenthesis are special characters (remember, they are used for grouping!)...

    That says that we want to match strings that have a left parenthesis, three characters between zero and nine, a right parenthesis, three characters between zero and nine, a dash, and then four characters between zero and nine. Only strings that match this strict guideline will be found with our regular expression search.

    Another property, IgnoreCase, which is false by default, determines if we want our search to be case sensitive. The final property of the regexp object is Global, which determines if a regular expression should search the entire string for multiple matches, or if it should just be satisfied with the first match it finds. Multiple matches are searched for when Global is true, and only match is searched for if Global is false.

    So, let's set these properties:

    objRegExpr.Pattern = "\([0-9]{3}\)[0-9]{3}-[0-9]{4}" objRegExpr.Global = True objRegExpr.IgnoreCase = True

    The regexp object has three methods, but I am only going to focus on one of them right now. The Execute method searches for the pattern specified by the Pattern property in the string it is passed. It returns a collection of Matches. So, let's define the string that we want to use our regular expression to search on:

    'What string are we searching on? Dim strSearchOn strSearchOn = "My phone number is (123)654-3211. Sue's phone " & _ "number is (873)392-1222." 'Declare a variable to hold our collection of Matches Dim colMatches 'Now, Execute the regular expression search Set colMatches = objRegExpr.Execute(strSearchOn)

    The above code creates the string we are going to search (strSearchOn), and executes the search. The Execute method returns a collection of Matches, which we assign to our variable colMatches. You may be wondering what a Match is. Well, it is another object that represents all of the strings we found. In our example, we would have found two matches, "(123)654-3211" and "(873)392-1222".

    Now, let's say that we want to display all of the matching strings... easy enough, we just need to step through the Matches collection and display the each match!

    Dim objMatch 'Print the # of matches we found Response.Write colMatches.Count & " matches found...<P>" 'Step through our matches For Each objMatch in colMatches Response.Write objMatch.Value & "<BR>" Next 'Clean up Set colMatches = Nothing Set objRegExpr = Nothing

    The above code will print out the number of matches we found, as well as each match.

    Well, that's it! I hope you've learned a lot and are now excited about using regular expressions in your code! I will definitely follow this article up with other, related articles, so stay tuned! In closing, let me highly recommend that you check out Microsoft Beefs up VBScript with Regular Expressions, an article available on Microsoft's site.

    Happy Programming!

  • By Scott Mitchell


  • Read Part 1


    Attachments:

  • Source code to the example in this article in text format...


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