I was in need to automate the serial transfer of a .bin file to an xbee with xmodem so I used this sloppy bash code:
echo "Starting connection..."
screen -d -m -S uart_con /dev/ttyO1 115200
screen -S uart_con -X stuff 'F'$(echo -ne '\015')
screen -S uart_con -X exec \!\! sz -X /home/file_directory/example.abs.bin
echo "now transfering... "
The third line sends a command to the other side(xbee) to start listening for a file transfer. So you are probably good with just:
screen -d -m -S uart_con /dev/ttyUSB0 115200
screen -S uart_con -X exec \!\! sz -X /path_to_file/example.file