awk '{print $4}' /path/to/file | grep string | sed -e 's/part_of_string_to_remove//g'
awk '{print $4}' /path/to/file | grep string | tr -d 'part_of_string_to_remove'
awk '{print $4}' /path/to/squid/access_log | grep cloudfront | sed -e 's/\:443\"//g' awk '{print $4}' /path/to/squid/access_log | grep cloudfront | tr -d ':443"'
$4 = 4th colum
cloudfront = string to search
:443″ = part of string to omit before output