How to list the system certificates on Linux?

Here is a way to list a summary of the certificates present in the /etc/ssl/certs/ca-certificates.crt file:

$ awk -v decoder='openssl x509 -noout -subject -enddate 2>/dev/null' '
  /BEGIN/{close(decoder)};{print | decoder}
' < /etc/ssl/certs/ca-certificates.crt