Regular Expressions to Match an XML Element
Regular Expressions are a powerful method used to parse text; this includes finding XML elements in your code. When you have particularly large files of any kind, finding text within them manually can be extremely time-consuming. Regular Expressions allow you to automate the process, in scripting languages like Perl, to save you time. Regular expressions are not limited to Perl, but each language that implements them has a slightly different syntax.
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Straightforward
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Create your regular expression. For example, if your XML element was "bookstore" then you know its opening tag is "<bookstore>" and to match it, your regular expression would look like this:
<bookstore>
Since the match needs to be exact, your regular expression doesn't need to accommodate for different variables or anything out of the ordinary.
Paired Tags
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Create a regular expression that will match both the beginning and ending tags of your XML element. Since we're still using "bookstore" here, the regular expression would look like this:
<bookstore>|</bookstore>
This will match both the opening and closing tags of your element.
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Varied Tags
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Create a regular expression that will match the XML elements that share similar names. If you had a number of "bookstore" elements to match, your regular expression could look like this:
<bookstore[0-9]*>
This will match any opening "bookstore" elements including those that have numbers after them. If you wanted to also match the ending tags, you could expand on the expression:
<bookstore[0-9]*>|</bookstore[0-9]*>
Vague Tags
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Create a regular expression that will match any XML element with an underscore. It's a good idea to make elements descriptive using the "_" character if you can. The expression would look like this:
<[a-z]+[0-9]*_[a-z]+[0-9]*>
This expression will match any XML element that has an underscore, as well as any numbers following either the prefix or suffix. If you wanted to make a regular expression to find any XML element at all, you could use:
<[a-z]+[0-9]*>
This expression will match any XML element, including those with numbers. There is no way to differentiate between XML elements and other built in tags however, since an XML element can be named anything that doesn't begin with a number. You will need to create a more specific regular expression to find those tags. This can be accomplished if you use a naming scheme, such as the underscore example earlier, with all your XML elements.
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