Find/Replace in xml file, with name/value pairs

Question

I'm trying to write a shell script which will take, as input, a set of name/value pairs and an XML file.

The aim is to search within the XML file for the "name" string from the name/value pairs file (demarcated with tags), and replace the "value" string defined at the same level of the XML file (demarcated with tags).

eg

Name/value pairs file

trousers=blue
hat=red
shoes=brown

Input XML file

<application>
    <Pairs>
        <Pair>
            <name>trousers</name>
            <value>black</value>
        </Pair>
        <IrritatingExtraLayer>
            <Pair>
                <name>hat</name>
                <value>green</value>
            </Pair>
        </IrritatingExtraLayer>
        <Pair>
            <name>shirt</name>
            <value>orange</value>
        </Pair>
    </Pairs>
</application>

Expected output file

<application>
    <Pairs>
        <Pair>
            <name>trousers</name>
            <value>blue</value>
        </Pair>
        <IrritatingExtraLayer>
            <Pair>
                <name>hat</name>
                <value>red</value>
            </Pair>
        </IrritatingExtraLayer>
        <Pair>
            <name>shirt</name>
            <value>orange</value>
        </Pair>
    </Pairs>
</application>

I have already created a script which can do this using xmlstarlet, however it is very slow (the files I am working with are thousands of lines long). The main code snippet (ignoring pre-processing and post-processing) from my script is:

for line in ${namevaluepairs}; do
                name=$(echo ${line} | cut -d'=' -f1)
                value=$(echo ${line} | cut -d'=' -f2)

                outputxml=$(echo ${outputxml} | xmlstarlet ed -u "//Pair/[name='${name}']/value" -v "${value}" )
done

What can I do to improve this?

Answer 1

I usually use xsh for similar tasks. I would be interested how fast the following compared to the xmlstarlet.

perl { 
    open $FH, '<', 'namevalues' or die $!;
    while (<$FH>) {
        chomp;
        ($n, $v) = split /=/;
        $h->{$n} = $v;
    }
} ;
open 1.xml ;
for //name {
    $v = xsh:lookup('h', text()) ;
    if $v set ../value $v ;
}
save :b ;

The trick is to store the name-value pairs in a hash (map, dictionary), then process all the names and retrieve the corresponding values from the hash.