Abstract
In some search operations in calibre one can use an xpath expression to get the values for particular tags, i.e. the following expression:
//h:div[re:test(@class, "figbox", "i")]
selects the content of a "div" tag whose "class" attribute is set to "figbox", so in the following html line:
<div class="figbox">Volterra</div>
the preceding xpath expression returns the value "Volterra". This is useful to compile the ToC of a book and for other tasks.
Question
Now, with the following processing-instructions
<?bag value="2" content="Volterra"?>
<?bag value="3" content="Ferrara"?>
which xpath expression can I use to obtain the value "Ferrara" but not "Volterra"?
Fieldwork
With the calibre editor I've tried putting in a book the following line
<?bag value="3" content="Ferrara"?>
and testing the following expressions to add the word "Ferrara" in the ToC:
//processing-instruction("bag")[@value="3"]/@content
substring-before(substring-after(//processing-instruction('bag'), 'value="3" content="'), '"')
but in both cases I get only
"calibre, version 3.30.0
ERROR: No items found: No items were found that could be added to the Table of Contents.
