In the following example I use openssl to connect to www.thawte.com, but I do not provide a location to find root certificates. I’m reading a great book on Apache security. One of the examples involves using the openssl client program to analyze a chain of certificates. The following example is a simple example of the use of openssl in the context of the book. The certificate analyzer is called opensl s_client -port 443 – and the client program is called openssl.”]
Source: https://taosecurity.blogspot.com/2006/09/using-root-certificates-with-openssl.html