If passphrase contains string termination char then how do I give this as an input in cmd line

开发者_JS百科openssl.exe rsa in prv.key -passin pass:MYPASS@123 -text

This will fail because My actual password is MYPASS@123\0

Can u please suggest how to give string termination char in cmd line

You can't. There is no way to pass a literal '\0' through a command line -- it is treated as a string terminator in multiple places before it reaches the library.

Presumably you found some other way to input that character to an OpenSSL password prompt. You'll need to use that method to decrypt the key and re-encrypt it with something more typeable.