sed -ne

sed -n
sed -e

• echo -n | openssl s_client -connect HOST:PORTNUMBER | sed -ne '/-BEGIN CERTIFICATE-/,/-END CERTIFICATE-/p' > /tmp/$SERVERNAME.cert

See also

• sed, gsed, -n, -i, Ansible: replace, append, Chef: Editing a file‎‎, lineinfile

https://serverfault.com/questions/139728/how-to-download-the-ssl-certificate-from-a-website