#!/bin/bash
url='http://w...content-available-to-author-only...h.com'
condition='^(https?://)?[[:alnum:]_.-]+(\.[[:alnum:]_.-]+)+[][[:alnum:]._~:/?#@!$&'"'"'*+,;=.-]+$'
if [[ "$url" =~ $condition ]]
then
    echo fine
else
    echo bad
fi