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How do you format an XML document to make it easy to read element attributes?

I have a xml based webservice that returns one or two elements, but with hundreds of attributes. As I'm doing development, I sometimes need to debug this service, but it can be hard since the output is just one blob.

Consider this:

$ echo '<root><foo z="26" y="25" x="24" a="1" b="2" c="3" d="something more"/></root>' | xmllint --format -
<?xml version="1.0"?>
<root>
  <foo z="26" y="25" x="24" a="1" b="2" c="3" d="something more"/>
</root>

I have found that tr works pretty good, but not ideal:

$ echo '<root><foo z="26" y="25" x="24" a="1" b="2" c="3" d="something more"/></root>' | xmllint --format - | tr ' ' \\\n
<?xml
version="1.0"?>
<root>


<foo
z="26"
y="25"
x="24"
a="1"
b="2"
c="3"
d="something
more"/>
</root>

Ideally the output would be something in between the xmllint and a funky hack

<?xml version="1.0"?>
<root>
  <foo
    z="26"
    y="25"
    x="24"
    a="1"
    b="2"
    c="3"
    d="something more"/>
</root>

That way i can grep for things, or sort or whatever.

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2
  • You are already using an XML parser, use that to query instead of trying to abuse sed/grep/awk. Alternatively, use xmlstarlet instead of xmllint.
    – Adrian Frühwirth
    Commented Apr 23, 2014 at 9:31
  • @AdrianFrühwirth, my goal is to make a script that I could call like curl, but would format the response cleanly. That way I can do formattedCurl.sh http://foo/service | grep prop | sort. You're right I can use xmllint's xpath functionality, but the trick is the XML data from the service is not consistent. I tried xmlstartlet format, but it appears to work exactly like xmllint -format. Perhaps I should look into rendering the document with xslt, or perhaps a carefully crafted sed or awk statement.
    – mlathe
    Commented Apr 23, 2014 at 16:51

2 Answers 2

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I would strongly urge away from grep/sed - they don't work for XML.

But fortunately, perl and XML::Twig have all sorts of magic for reformatting and extracting values as you wish. get_xpath works nicely for extracting a value, or you have twig_handlers to handle elements depending on use case. (Or just iterate using children or similar).

But anyway - to format your XML:

#!/usr/bin/perl

use strict;
use warnings;

use XML::Twig;

my $twig = XML::Twig->new(
    pretty_print  => 'nsgmls',
);
$twig->parse (\*DATA);
$twig->print;


__DATA__
<?xml version="1.0"?>
<root>
  <foo
    z="26"
    y="25"
    x="24"
    a="1"
    b="2"
    c="3"
    d="something more"/>
</root>

in nsgmls printing, this gives:

<?xml version="1.0"?>
<root
><foo
a="1"
b="2"
c="3"
d="something more"
x="24"
y="25"
z="26"
/></root>

indented_a gives you:

<?xml version="1.0"?>
<root>
  <foo
      a="1"
      b="2"
      c="3"
      d="something more"
      x="24"
      y="25"
      z="26"
  />
</root>

Which seems to be pretty close to what you're seeking?

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2
  • Is there a way to keep XML::Twig from alphabetizing the attributes?
    – Alexej Magura
    Commented Apr 20, 2017 at 15:55
  • Yes. When calling new set keep_atts_order => 1. But you should be wary of anything that breaks if the ordering of attributes changes, because it's not parsing XML correctly.
    – Sobrique
    Commented Apr 25, 2017 at 10:17
0

You could use the fantastic BeautifulSoup Python library. This code sample retrieves an XML file from a URL given as input argument to the script, parses it using LXML and then pretty prints it.

#!/usr/bin/env python
import sys
import urllib2
import bs4

soup = bs4.BeautifulSoup(urllib2.urlopen(sys.argv[1]), ["lxml", "xml"])
print(soup.prettify())

If you don't have access to LXML, you could try without ["lxml", "xml"], though this will parse the data als HTML rather than XML and is not the proper way.

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