Does elegance = performance ?

#!/bin/sh

if [ $# -gt 0 ];
then
        directory="$1"
        shift 1
else
        printf "usage: %s directory|file ['*.ext']\n" "$(basename "$0")" >&2
        exit 1
fi

if [ $# -lt 1 ];
then
        extensions="*"
else
        extensions="$1"
fi

if [ -d "${directory}" ];
then
        find "${directory}" -name "${extensions}" -type f \
                -exec wc -l {} \; \
                | awk '{ SUM += $0 } END { print SUM }'
else
        wc -l "${directory}" | cut -d' ' -f 1
fi


...


#!/bin/sh

([ $# -gt 0 ] && [ -d "$1" ] && [ -n "$2" ] && \
for i in $(ls -1 "$1"/*.$2); do
        a=$(($a+$(wc -l < "$i")))
        #or a+=$(wc -l < "$i") if you use bash lol
done && echo $a) || printf "Usage: %s <an existing directory> <a file extension>\n" "$0" >&2 && exit 1