Useful when migrating. Point at source DB instance, retrieve grants using this script, pipe through the Add a semicolon in PERL script, and voila, recreate grants on destination instance.

#!/bin/bash 
( 
 mysql --batch --skip-column-names -e "SELECT user, host FROM user" mysql 
) | while read user host 
do 
  echo "# $user @ $host"
  mysql --batch --skip-column-names -e"SHOW GRANTS FOR '$user'@'$host'"
done