Nevermind, this works:
#!/bin/bash
FILE_TO_UPLOAD="$1"
ARDUINO_DIR="/Applications/Arduino"
for CUR_PORT in $(find /dev/tty.usbserial*)
do
echo "$CUR_PORT"
/Applications/Arduino.app/Contents/Resources/Java/hardware/tools/avr/bin/avrdude -C/Applications/Arduino.app/Contents/Resources/Java/hardware/tools/avr/etc/avrdude.conf -v -v -v -v -patmega328p -carduino -P"$CUR_PORT" -b115200 -D -V -Uflash:w:"$FILE_TO_UPLOAD":i
done