Looking Out To Sea

The stream editor sed is a great tool for automating text editing — replacing names, date or other statements in a high-speed, programmable fashion.

One thing it isn’t really cut out for is XML because the structure of XML is not line-oriented. If you want to automate XML editing quickly I totally recommend XML Starlet for the job. You can replace node names, attributes, values and so on nested deep inside an XML document while paying full heed to namespaces and such.

On top of that it also lets you see a simple overview and to select values out of documents. Once you get the hang of it you can do some really nice things. I recently got it to rewrite some version numbers inside an Eclipse .cproject file and the resulting script is about as readable and concise as you could hope for.

xmlsed()
{
    ATTRIBUTE=$1
    VALUE=$2
    # A quick hack to update build variables used for debug images.
    xmlstarlet edit --inplace --update \
        '//storageModule[@name="Debug"]/macros/stringMacro[@name="'$ATTRIBUTE'"]/@value' \
        -v $VALUE .cproject
}

xmlsed DATE_DD $(date +'%d')
xmlsed COMPILEDBY $USER

Looking at the examples I have barely touched the surface of what can be done with this tool but I’m already pretty impressed with what can be achieved.