How to add text before values in xml?

Question

Here is my test.xml file:

<?xml version="1.0"?>
<path>
  <dir name="directory">
    <file name="file1"/>
    <file name="file2"/>
  </dir>
</path>

Now I can add some text after my values:

xmlstarlet ed -s "//file[@name]/@name" -t text -n "@name" -v "_copy_" test.xml

Result:

…
<file name="file1_copy_"/>
<file name="file2_copy_"/>
…

How can I add a text before values?

…
<file name="_copy_file1"/>
<file name="_copy_file2"/>
…

Answer 1

According to the command line help, with xmlstarlet ed, you can use the update -u option and include a replacement XPath expression -x:

xmlstarlet ed -u <xpath> -x <xpath>

In the replacement expression you can use an XPath concat() function to generate the string which will replace the attribute. The expression concat('_copy_',.) will concatenate the string '_copy_' before the current node, which is the attribute you are selecting. Your expression should be:

 xmlstarlet ed -u "//file[@name]/@name" -x "concat('_copy_',.)" test.xml