Recently, I needed to find the corresponding public key from a private key (
.pem) to give a Linux user access to a server. I used the below code to generate the public key.
ssh-keygen -y -f privatekey > publickey
This code generates an OpenSSL key, which wasn't what I needed in that specific case, but might also come in handy.
openssl rsa -in privatekey -pubout > publickey