I am trying to search for a specific node in an XML file using XPath. This search worked just fine under REXML but REXML was too slow for large XML docs. So moved over to LibXML.
My simple example is processing a Yum repomd.xml file, an example can be found here: http://mirror.san.fastserv.com/pub/linux/centos/6/os/x86_64/repodata/repomd.xml
My test script is as follows:
require 'rubygems'
require 'libxml'
p = LibXML::XML::Parser.file( "/tmp/dr.xml")
repomd = p.parse
filelist = repomd.find_first("/repomd/data[@type='filelists']/location@href")
puts "Length: " + filelist.length.to_s
filelist.each do |f|
puts f.attributes['href']
end
I get this error:
Error: Invalid expression.
/usr/lib/ruby/gems/1.8/gems/libxml-ruby-2.7.0/lib/libxml/document.rb:123:in `find': Error: Invalid expression. (LibXML::XML::Error)
from /usr/lib/ruby/gems/1.8/gems/libxml-ruby-2.7.0/lib/libxml/document.rb:123:in `find'
from /usr/lib/ruby/gems/1.8/gems/libxml-ruby-2.7.0/lib/libxml/document.rb:130:in `find_first'
from /tmp/scripty.rb:6
I have also tried simpler examples like below, but still no dice.
p = LibXML::XML::Parser.file( "/tmp/dr.xml")
repomd = p.parse
filelist = repomd.root.find(".//location")
puts "Length: " + filelist.length.to_s
In the above case I get the output:
Length: 0
Your inspired guidance would be greatly appreciated, and I have searched for what I am doing wrong, and I just can't figure it out...
Here is some code that will fetch the file and process it, still doesn't work...
require 'rubygems'
require 'open-uri'
require 'libxml'
raw_xml = open('http://mirror.san.fastserv.com/pub/linux/centos/6/os/x86_64/repodata/repomd.xml').read
p = LibXML::XML::Parser.string(raw_xml)
repomd = p.parse
filelist = repomd.find_first("//data[@type='filelists']/location[@href]")
puts "First: " + filelist
In the end I reverted back to REXML and used stream processing. Much faster and much easier XPath syntax implementation.