When you use sed to insert a template file into another file with the command
# $1 String to insert
# $2 File to insert to
# $3 String to insert after
sed "/$3/a\\
$1\\
" $2 > tmp && mv tmp $2 and get the error message
extra characters at the end of n command
Make sure the template file supplied in $1 does not have an empty line at the top.