Is it possible to copy the output of linux terminal with the keyboard only

I am trying to write a macro to connect to my school's workstations. I am trying to copy a single number from the output of another command. For example, the output is something like: vnc viewer: -via username@address :5, where the 5 is the port. Is it possible to copy the number 5 from just keyboard inputs? Or, alternatively, is it possible to copy the output of a command to the clipboard so I can paste it somewhere else?