If cmd is not an empty string, screen will not use the terminal capabilities
po/pf for printing if it detects an ansi print
ESC [ 5 i, but pipe the output into cmd.
This should normally be a command like ‘lpr’ or
‘cat > /tmp/scrprint’.
Printcmd without an argument displays the current setting.
The ansi sequence
ESC \ ends printing and closes the pipe.
Warning: Be careful with this command! If other user have write access to your terminal, they will be able to fire off print commands.