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XML CDATA and escaping

October 25th, 2007 tonyg

XML’s syntax for CDATA looks like this:

  <![CDATA[some text]]>

Tag syntax within a CDATA section is suspended, so this is well-formed XML:

  <![CDATA[some <more> text]]>

even though it looks like the “<more>” tag is unclosed.

There’s only one thing you can’t say in a CDATA section: “]]>”. But there’s a trick to save us, even here. To print an arbitrary string in a CDATA enclosure, replace each instance of “]]>” with “]]]]><![CDATA[>”, and then put the normal “<![CDATA[”/”]]>” brackets around it:

  my ]]> text

becomes

  <![CDATA[my ]]]]><![CDATA[> text]]>

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