Piping an interactive session to a file

Question

I have made a toy interactive console program that is basically an interpreter:

$ myprogram
> this is user input
this is program output

Answer 1

As two processes can't read the same input two tees are needed, one which reads terminal input and writes to program standard input and file.log another which reads program standard output and writes into terminal output and file.log:

tee -a file.log | program | tee -a file.log