function main() {
let str = "Hello YouQuant!"
let file = os.open("data.txt", "w+")
file.write(str)
// If i > str.length: will throw InternalError: seek .../xxx/data.txt: invalid argument at main
for (let i = 1; i <= str.length; i++) {
file.seek(-i, 2)
let data = file.read(1)
Log("i:", i, ", data:", data)
}
file.close()
}