Platform detection in bash without external executables (no /bin/uname)

bash_uname.sh

#!/usr/bin/env bash
# Example to detect OS in bash using bash built-in variable $OSTYPE instead of `uname`

# platform differences 
stty_f="-F" SERIAL_TTY_PREFIX=ttyUSB # Default (Linux)
case "${OSTYPE,,}" in
	*bsd*) stty_f="-f" SERIAL_TTY_PREFIX=ttyU ;; # FreeBSD/NetBSD/OpenBSD/etc
	darwin*) stty_f="-f" SERIAL_TTY_PREFIX=cu.usbserial- ;; # Mac OSX
esac

x=(/dev/${SERIAL_TTY_PREFIX#/dev/}*)
PS3="Which serial port? "
select PORT in ${x[*]} ;do [[ -c "$PORT" ]] && break ;done

echo "stty ${stty_f} $PORT 19200"