Add stdin reading capabilities.

src/main.rs

@@ -1,12 +1,19 @@
+use std::io::Read;
+
 fn main() {
     let args: Vec<String> = std::env::args().collect();
 
-    if args.len() < 2 {
-        eprintln!("Missing arguments: <IP>.");
-        std::process::exit(1);
-    }
-
-    let ip_string = &args[1];
+    let mut input_buf = String::new();
+    let ip_string = if args.len() < 2 || args[1] == "-" {
+        if std::io::stdin().read_to_string(&mut input_buf).is_ok() {
+            &input_buf
+        } else {
+            eprintln!("Missing arguments: <IP>.");
+            std::process::exit(1);
+        }
+    } else {
+        &args[1]
+    };
 
     println!(
         "Result: \n{}",
@@ -14,7 +21,7 @@ fn main() {
             Ok(x) => {
                 int_to_ip(x)
             }
-            Err(_) => ip_to_int(ip_string).to_string(),
+            Err(_) => ip_to_int(ip_string.trim()).to_string(),
         }
     );
 }