I wrote this simple tool because I was sometimes receiving S/MIME signed messages with non-detached signatures that couldn't be easily read in console mail readers (e.g. in pine). Of course I could have used openssl smime command line tool, but it needs some weird parameters to work. So I took this opportunity to write something that uses the OpenSSL library.
It can work either as a filter in which case it doesn't take any argument, or it can take a filename as an argument.