mtaylor:~ Matt$ cat usb-serial.sh
#!/bin/sh
# By Matt Taylor.

DEV=`ls /dev/tty.usb*|head -n1`

if [ -z $DEV ]; then
    echo "Error: USB to Serial device not found in /dev/tty.* - please make sure it's connected"
    exit
else
    echo "Device found: $DEV"
fi

if [ `ps a |  grep 'dev/tty.'| grep -v 'grep' | awk '{print$1}'|wc -l` -gt 0 ]; then
    read -p "Error: $DEV is currently in use, kill existing sessions? [y/n] " CHECK
    if [ $CHECK == "y" ]; then
        echo "Killing existing pids.."
        ps a |  grep 'dev/tty.'| grep -v 'grep' | awk '{print$1}' | xargs kill -9
        screen -wipe
    else
        echo "Exiting"
        exit
    fi
fi

if [ -z $1 ]; then
    echo "Baud rates: 4800 9600 19200 38400 57600 115200 31250"
    read -p "What baud rate do you want to use? " BAUD
else
    BAUD=$1
fi

screen -U $DEV $BAUD