Replace specific tags in xml in unix

Question

I would like to replace specific values (Not for all elements). Here all are having same Background_color, but i do not want to replace Background_color for only specific one. How can we implement? This is just a sample code.(I would have list of skin names in file for which i should not replace the Background_color)

            <Skins>
             <skin>
               <att name="Name" value="sknLblG3S3" type="String"/>
               <att name="WidgetType" value="Label" type="String"/>
               <att name="Background_color" value="228,221,213" type="RGB"/>
            <skin>
            <skin>
              <att name="Name" value="name" type="String"/>
              <att name="WidgetType" value="Label" type="String"/>
              <att name="Background_color" value="228,221,213" type="RGB"/>
            <skin>
            <skin>
              <att name="Name" value="sknLblG3S5" type="String"/>
              <att name="WidgetType" value="Label" type="String"/>
              <att name="Background_color" value="228,221,213" type="RGB"/>
            <skin>
            <skins>

Answer 1

Assuming your XML is in fact valid (your sample isn't - I've had to fix some of the tags by hand) - Then you should use an XML parser. As you've tagged perl, I'll assume a perl answer is acceptable:

#!/usr/bin/env perl
use strict;
use warnings;
use XML::Twig;

my $twig = XML::Twig->parsefile( 'your_file.xml' );

#find and iterate all the 'skin' elements. 
foreach my $skin ( $twig->get_xpath('//skin') ) {
    #Check the 'att' element with these particular attributes. E.g. Name, sknLblG3S3
    if ( $skin->get_xpath('./att[@name="Name"][@value="sknLblG3S3"]') ) {
        #select the att with a name of 'Background_Colour' 
        my $bg_att = $skin->get_xpath( './att[@name="Background_color"]', 0 );
        #modify the attribute 'value'. 
        $bg_att->set_att( 'value', "123,456,789" );
    }
}

#set output formatting - note, this can break with certain XML elements, which you don't seem to have. 
$twig->set_pretty_print('indented');
$twig->print;

You could iterate the att elements with $skin -> children() if you find it easier to read, and the att method in XML::Twig reads attributes. I feel xpath is clearer in this example though.

(You can also probably do a more complicated xpath statement to match children/siblings, but I'm not sure that'd help readability).

Answer 2

In awk, you could try this

awk -F"=?\"?[ ]*" 'BEGIN{replace="sknLblG3S3"; newcolor="0,0,0"}
                   $4=="Name"{name=$6}
                   ($4=="Background_color" && match(replace, name))
                      {gsub(/value="[0-9,]*"/, "value=\""newcolor"\"");}
                   {print;}' inputFile

You have to define two variables in the BEGIN-block:

• replace: The skin name(s) to be replaced, e.g., replace="name,sknLblG3S3"
• newcolor: The new background color