openssl x509
命令手册OpenSSL command to manage X.509 certificates. More information: https://www.openssl.org/docs/manmaster/man1/openssl-x509.html.
openssl x509 -in {{filename.crt}} -noout -text
openssl x509 -enddate -noout -in {{filename.pem}}
openssl x509 -inform {{der}} -outform {{pem}} -in {{original_certificate_file}} -out {{converted_certificate_file}}
openssl x509 -in {{certificate_file}} -noout -pubkey -out {{output_file}}