run this file with sudo

changebr.rs

use std::env;
use std::fs;
fn main() {
    let max_brightness: i32 = 800;
    let args: Vec<String> = env::args().collect();
    let path = "/sys/class/backlight/intel_backlight/brightness";
    //let content = &args[1].as_bytes();
    let mut str = "down";
    if args.len() == 2 {
        str = &args[1].trim();
    }

    let data = fs::read_to_string(path).expect("Error in reading data");

    let mut current_brightness: i32 = data.trim().parse().unwrap();
    let step = 40;

    match &str[..] {
        "up" => current_brightness += step,
        "down" => current_brightness -= step,
        _ => current_brightness = 100,
    }

    if current_brightness > max_brightness {
        current_brightness = max_brightness;
    }

    if current_brightness < 50 {
        current_brightness = 50;
    }

    let br = current_brightness.to_string();

    fs::write(path, br.as_bytes()).expect("Unable to write data to brightness");
}