Useful for decoding email message attachments
Source: http://superuser.com/questions/120796/os-x-base64-encode-via-command-line
openssl base64 -d -in <infile> -out <outfile>
OR
cat <filename> | openssl base64 -d
openssl base64 -in <infile> -out <outfile>
openssl
is installed by default on Mac OS X
I gathered some list of possible bas64 solutions https://gist.github.com/stokito/18ce554bd53bdb6355670066d5ae9943