I have published a detailed answer here: https://forums.gentoo.org/viewtopic-p-8132756.html#8132756

Here is the short version:

#!/bin/bash
MySerialPort="/dev/ttyUSB0"
MyLatency="2"
echo "#include <fcntl.h>
#include <sys/ioctl.h>
main()
{ int fd; fd = open(\"${MySerialPort}\",O_RDWR | O_NOCTTY ...