take tty path as arugment

src/bin.rs

@@ -2,13 +2,17 @@ use mhz19::MHZ19;
 use std::time::Duration;
 use std::thread::sleep;
 use std::ffi::OsStr;
+use std::env;
 
 const DELAY: Duration = Duration::from_secs(1);
 
 fn main() {
-    loop {
+    match env::args().skip(1).next() {
-        listen("/dev/ttyUSB0");
+        Some(path) => loop {
+            listen(&path);
             sleep(DELAY);
+        },
+        None => eprintln!("Path required")
     }
 }