| Page Item | Value |
| Title | Regular Expressions with VBScript and Visual Basic 6.0 |
| Description | Using Regular Expressions with VBScript and Visual Basic 6.0 - a brief introduction |
| Keywords | tutorial, example, asp, active server page, visual basic, vbscript |
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Home Articles ASP Programming Articles Regular Expressions with VBScript and Visual Basic 6.0 From a programming perspective, one of the biggest annoyances I have faced with VBScript is the lack of decent string handling functions. Sure, with a bit of imagination, functions such as InStr, Left and Mid can be combined to help with the job at hand. But for anyone used to the Perl programming language, VBScript can appear to be extremely inflexible. VBScript Regular Expressions While still being someway off the effectiveness of Perl, version 5 of VBScript now has much improved text handling functions, through it's support for Regular Expressions. For anyone who hasn t encountered the term, Regular Expressions have been an essential part of that nasty operating system known as Unix for many years (and where considered so useful that they were incorporated into Perl). They can be cryptic and difficult to learn, but they allow sophisticated pattern matching in strings. Regular Expressions are quite involved (it is possible to buy whole books devoted to their use!), and the purpose of this article is simply to draw your attention to the potential of using them within VBScript. If you want to know more, then try some of the references at the bottom of the article. Using the VBScript RegEx object Support for Regular Expressions has been included in VBScript by the inclusion of the RegExp object in VBScript version 5. This is the version of the VBScript scripting engine released with Internet Explorer 5. If you don t have IE5 on your server, but want to upgrade the scripting engine, then download the new scripting engine from www.microsoft.com/scripting . If you don t know which version of the scripting engine you are using, then try using the following small script: % Response.Write You are using Response.Write ScriptEngine Response.Write version ScriptEngineMajorVersion . ScriptEngineMinorVersion % This should display a message such as the one below: Using the RegExp object Once you have determined that your web server is running the correct version of VBScript, the following lines of code will demonstrate the use of the RegExp object. The first line of code will create a new string that will be searched for the existence of a sub-string: StringToSearch = http://www.brettb.com The RegExp object can then be created: Set RegularExpressionObject = New RegExp This object has three properties: Pattern, IgnoreCase and Global. Pattern specifies the Regular Expression that should be searched for. IgnoreCase should be True or False depending on whether the search should be case sensitive (the default is true). Finally, the Global property should be set to True if the search should match all occurrences of the pattern, or False if just the first occurrence should be matched: With RegularExpressionObject .Pattern = .com .IgnoreCase = True .Global = True End With Once the RegExp object s properties have been set, it is time to test the Regular Expression. This is done using something like the line below. This uses the Test method of the RegExp object to see if the Regular Expression is found in the StringToSearch string. expressionmatch = RegularExpressionObject.Test(StringToSearch) The Test method will return True if the Regular Expression was found, and False if it was not found. If expressionmatch Then Response.Write RegularExpressionObject.Pattern was found in StringToSearch Else Response.Write RegularExpressionObject.Pattern was not found in StringToSearch End If Finally, the RegExp object is destroyed since it is no longer required. Set RegularExpressionObject = nothing More RegExp object methods As well as the Test method, the VBScript RegExp object has two further methods: Execute and Replace. The RegExp Execute method The RegExp Execute method is a more sophisticated version of the Test method. As well as seeing if the Regular Expression is found within a string, it will also return the number of matches made within that string, and at which position in the string the match(es) were made. An example of its use is below: % StringToSearch = The website ASPWatch.com contains lots of information about ASP, asp, as well as Asp. Set RegularExpressionObject = New RegExp With RegularExpressionObject .Pattern = ASP .IgnoreCase = False .Global = True End With Set expressionmatch = RegularExpressionObject.Execute(StringToSearch) If expressionmatch.Count 0 Then For Each expressionmatched in expressionmatch Response.Write B expressionmatched.Value /B was matched at position B expressionmatched.FirstIndex /B BR Next Else Response.Write B RegularExpressionObject.Pattern /B was not found in the string: B StringToSearch /B . End If Set RegularExpressionObject = nothing % As with the Test method, the RegExp s Global and IgnoreCase properties are useful. The RegExp Replace method This can be used to replace a part of a string using Regular Expression matching. For example, in the script below, .co.uk is changed into .com: % InitialString = www.foo.co.uk Set RegularExpressionObject = New RegExp With RegularExpressionObject .Pattern = .co.uk .IgnoreCase = True .Global = True End With ReplacedString = RegularExpressionObject.Replace(InitialString, .com ) Response.Write Replaced InitialString with ReplacedString Set RegularExpressionObject = nothing % Real life Regular Expressions So far, this article has shown how to use the VBScript RegExp object to manipulate and test strings, but there is nothing here that couldn t already be done with other VBScript functions. The power of Regular Expressions only become apparent when more complex situations are encountered. For example, the VBScript function below will strip out all the HTML tags from strings: % Function stripHTMLtags(HTMLstring) Set RegularExpressionObject = New RegExp With RegularExpressionObject .Pattern = [^ ]+ .IgnoreCase = True .Global = True End With stripHTMLtags = RegularExpressionObject.Replace(HTMLstring, ) Set RegularExpressionObject = nothing End Function % The function can then be called using something like: % Response.Write stripHTMLtags( B This I is /I TT style= background-color: rgb(0,255,255) some /TT FONT COLOR=#FF00FF HTML /FONT /B ) % The function works because it replaces HTML tags with a null character. HTML tags are identified using the Regular Expression held in the Pattern property. This is a sequence of special characters. This means that a HTML tag should start with a . It should then contain one or more characters except for a greater than sign . This is indicated by enclosing the greater than sign in square brackets, and using the plus sign (which means match the preceding character one or more times. The ^ symbol denotes that the character should NOT appear. Finally, it should contain a greater than sign to close the HTML tag. Looks complicated? Unfortunately most things that originate on Unix systems are! The best way to figure out Regular Expressions is to play around with them check the bottom of this article for guides to the various characters that can be used. As a further help, a couple more regular expressions are shown below: The dollar sign is used to look for matches at the end of a string, so the following will look for .co.uk at the end of a string: .Pattern = .co.uk$ Use a bar to specify that several expressions should be matched. The following will match .co.uk or .com at the end of a string: .Pattern = .co.uk$|.com$ Using Regular Expressions in Visual Basic Few people seem to know that Regular Expressions can also be used with Visual Basic 5 or 6. All you need to do is to include a reference to Microsoft VBScript Regular Expressions in your project. The following sample code will replace the HTML in the Text1 textbox with plain text: % Dim RegularExpressionObject As Object Set RegularExpressionObject = New VBScript_RegExp.RegExp With RegularExpressionObject .Pattern = [^ ]+ .IgnoreCase = True .Global = True End With Text1.Text = RegularExpressionObject.Replace(Text1.Text, ) Set RegularExpressionObject = Nothing % Further Reading The Regular Expression Laboratory is an assistant simple to use tool to help you learn and prepare regular expressions [ more details and trial version here ]. Subexpression substitutions in VBScript regular expressions - a more detailed look at complex text replacement operations. Microsoft Beefs up VBScript with Regular Expressions - Microsoft's guide to using Regular Expressions with VBScript. A list of special characters that can be used in Regular Expressions is available in the VBScript 5 Language Reference. (at msdn.microsoft.com/scripting). Regular Expression Library - A small but growing library of Regular Expressions suitable for use with VBScript. Useful Development Tools ASP Documentation Tool Automatically creates developer documentation for ASP 2.0 and 3.0 web applications written in VBScript and JScript. Documentation for Microsoft Access, SQL Server 7/2000 databases and Visual Basic 6.0 components associated with the web application can also be incorporated into the reports. Documentation is created in HTML, HTML Help and plain text formats. View Sample Output (HTML Help format). View Sample Output (HTML Format). Download Trial Version (5.2Mb ZIP file). ASP.NET Documentation Tool Automatically creates developer documentation for ASP.NET web applications written in C# or VB.NET. Documentation for SQL Server 7/2000 databases and C#/VB.NET components associated with the web application can also be incorporated into the reports. Documentation is created in HTML, HTML Help and plain text formats. View Sample Output (HTML Help format). View Sample Output (HTML Format). Download Trial Version (2.9Mb ZIP file). SQL Documentation Tool The SQL Documentation Tool creates technical documentation for Microsoft SQL Server 7.0 and 2000 databases. Technical documentation is created in HTML and HTML Help formats. The HTML Help format documentation is fully searchable and cross referenced. The SQL Documentation Tool documents SQL Server Tables, Views, Stored Procedures, Triggers and Table Relationships. View Sample Output (HTML Help format). View Sample Output (HTML Format). Download Trial Version (10.3Mb ZIP file). Index Server Companion The Index Server Companion is a Windows application that extends the functionality of Microsoft Index Server so that it is able to index content from remote websites and also from ODBC databases. As such it can be used as a low cost alternative to Site Server 3.0 Search. View Product Documentation (119K ZIP file). Try Sample Search Facility . Download Trial Version (1.7Mb ZIP file). The Website Utility The Website Utility examines websites for errors and areas that need to be optimised for search engines by using a built in web crawling engine. Errors checked for include broken or moved hyperlinks, missing page titles and missing meta tags. It also generates HTML for use in creating website site maps (table of contents pages - like this one ), and is able to create both client-side JavaScript Search Engines and server-side ASP Search Engines for a website. View Sample Output (HTML Help format). View Sample Output (HTML Format). 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