If you were writing a command line tool to process PSBTs, how would you handle accepting base 64 encoded PSBT strings?

1. as a command line argument? ( --psbt-base64 bUnChOfBaSe64... )

2. on stdin? (with a prompt, or not?)

3. Both? ( --psbt-base64 - means read from stdin, otherwise try to interpret the argument as base64 )