How to set the baud rate for Macs in a terminal

Minicom is an excellent tool that does exactly what you're asking for. You can get it using apt on ubuntu but should check this Tutorial out for Mac.

Keep the serial reset issue in mind if you plan on sending data to the Arduino. see http://arduino.cc/playground/Main/DisablingAutoResetOnSerialConnection

On Mac OS, stty seemingly can only change terminal settings for an ongoing access.

It works to either:

• Access the serial interface, e.g. cat /dev/cu.usbserial, the default settings will be used at first. On a different terminal use stty, e.g. stty -f /dev/cu.usbserial 230400 to set the baud rate, the settings of the terminal accessed before will change.

• There is a small time window after executing stty, in which the access can be performed with the desired parameters, e.g. stty -f /dev/cu.usbserial 230400 & cat /dev/cu.usbserial executes stty, detaches it and then immediately performs the access to the serial device.

• For one line command logging serial port /dev/tty.usbserial-X's output to cat.out and terminating the logging by pressing Ctrl+C, here is the solution: trap 'kill $(jobs -p)' SIGINT ; cat /dev/tty.usbserial-X | tee cat.out & stty -f /dev/tty.usbserial-X 115200. You can type Ctrl+C to terminate logging to cat.out. (edited)

This only seems to work for the /dev/cu.* device files. I don't know the difference from /dev/tty.* files.