[chaley]

S/R has both the template language and full regular expressions available, so there is very little you cannot do. See http://calibre-ebook.com/user_manual/template_lang.html and http://calibre-ebook.com/user_manual/regexp.html.

From your example you appear to be using the template language. To get the first 10 characters of a field, use {field:shorten(10,,0)}. To get the last 10, use {field:shorten(0,,10)}. The shorten function (and several others) is documented in the manual referred to above.

Note that you can also grab the first up-to-ten characters using a regexp. The search expression would be

(.{1,10}).*

The replace expression would be

\1