[grep] Count all occurrences of a string in lots of files with grep

Here is a faster-than-grep AWK alternative way of doing this, which handles multiple matches of <url> per line, within a collection of XML files in a directory:

awk '/<url>/{m=gsub("<url>","");total+=m}END{print total}' some_directory/*.xml

This works well in cases where some XML files don't have line breaks.