Open source command line tool for Linux to diff XML files ignoring element order

Question

Is there an open source command-line tool (for Linux) to diff XML files which ignores the element order?

Example input file a.xml:

<tag name="AAA">
  <attr name="b" value="1"/>
  <attr name="c" value="2"/>
  <attr name="a" value="3"/>
</tag>

<tag name="BBB">
  <attr name="x" value="111"/>
  <attr name="z" value="222"/>
</tag>
<tag name="BBB">
  <attr name="x" value="333"/>
  <attr name="z" value="444"/>
</tag>

b.xml:

<tag name="AAA">
  <attr name="a" value="3"/>
  <attr name="b" value="1"/>
  <attr name="c" value="2"/>
</tag>

<tag name="BBB">
  <attr name="z" value="444"/>
  <attr name="x" value="333"/>
</tag>
<tag name="BBB">
  <attr name="x" value="111"/>
  <attr name="z" value="222"/>
</tag>

So comparing these 2 files should not output any differences. I have tried to sort the files with XSLT first:

<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
  <xsl:output method="xml" encoding="WINDOWS-1252" omit-xml-declaration="no" indent="yes"/>
  <xsl:strip-space elements="*"/>

  <xsl:template match="node()|@*">
    <xsl:copy>
      <xsl:apply-templates select="node()|@*">
        <xsl:sort select="@*" />
      </xsl:apply-templates>
    </xsl:copy>
  </xsl:template>
</xsl:stylesheet>

But the problem is that for the elements <tag name="BBB"> there is no sorting. They are simply output the order which they are input.

I have already looked at diffXml, xDiff, XMLUnit, xmlstarlet but none of these solve the problem; the diff output should be human readable, e.g. like when using diff.

Any hints on how either the sorting or ignoring element-order diff can be solved? Thanks!

Answer 1

I had a similar problem and I eventually found: https://superuser.com/questions/79920/how-can-i-diff-two-xml-files

That post suggests doing a canonical xml sort then doing a diff. Being that you are on linux, this should work for you cleanly. It worked for me on my mac, and should work for people on windows if they have something like cygwin installed:

$ xmllint --c14n a.xml > sortedA.xml
$ xmllint --c14n b.xml > sortedB.xml
$ diff sortedA.xml sortedB.xml