XML Hacks

Transform XML Documents with grep and sed

Use grep and sed to transform XML instead of XSLT.

You can use a pair of good old Unix utilities, grep and sed, to transform XML. Both of these utilities allow you to search based on regular expressions, a powerful though sometimes complex language for searching sets of strings. This hack will provide some examples of how you can use regular expressions to transform XML documents.

Tip

This hack discusses regular expressions only as far as the examples given, but is not a tutorial on regular expressions.

grep

grep is a Unix utility, but it also runs on other platforms. If you have a Linux distribution, such as Red Hat (http://www.redhat.com), or if you have Cygwin on Windows (http://www.cygwin.com), grep is already available to you at the shell. You can also get the GNU distribution of grep from http://www.gnu.org, but you’ll have to compile the C code to get it to work. This hack uses Version 2.5 of grep.

Say, for example, you wanted to grab part of an XML document and create a new one; instead of using XSLT, you could use grep and regular expressions in some circumstances. If you are familiar with regular expressions, using grep to do such things may come easily to you. Take a look at time.xml :

<?xml version="1.0" encoding="UTF-8"?>
   
<!-- a time instant -->
<time timezone="PST">
 <hour>11</hour>
 <minute>59</minute>
 <second>59</second>
 <meridiem>p.m.</meridiem>
 <atomic signal="true"/>
</time>

If you just want to extract the XML declaration, ...