Found a helpful article today, The Most Common OpenSSL Commands.

The particular command I needed wasn’t listed there though. What I needed to do was examine the contents of my Certificate Revocation List (CRL) certificate. I had a problem connecting to my website because it was complaining about an expired certificate and the culprit was indeed the CRL as I discovered when I ran:

 $ openssl crl -inform CER -in ca.crl -text -noout