I forget where I found this, so if anyone wants to claim attribution, let me know and I'll add a line here.  If put into `/etc/profile.d/serial-console.sh`, the following will auto size a serial terminal windows size and create a function for manually adjusting later.  Since I access RPIs and BBBs via the serial console, their tty names are already listed in the case statement; add others if your system is different. rsz helps when you later reconnect and minicom or screen is in a different sized window...

        rsz() {
            if [[ -t 0 && $# -eq 0 ]];then
                    local IFS='[;' escape geometry x y
                    echo -ne '\e7\e[r\e[999;999H\e[6n\e8'
                    read -sd R escape geometry
                    x=${geometry##*;} y=${geometry%%;*}
                    if [[ ${COLUMNS} -eq ${x} && ${LINES} -eq ${y} ]];then
                            echo "${TERM} ${x}x${y}"
                    else
                            echo "${COLUMNS}x${LINES} -> ${x}x${y}"
                            stty cols ${x} rows ${y}
                    fi
            else
                    print 'Usage: rsz'
            fi
        }


        case $( /usr/bin/tty ) in
                /dev/ttyAMA0|/dev/ttyO0|/dev/ttyS0) export LANG=C
                                                    rsz
                                                    ;;
        esac