Read from stdin, write to stdout

src/main.rs

@@ -1,3 +1,10 @@
+use std::io::{self, Read, Write};
+
 fn main() {
-    println!("Hello, world!");
+    let mut stdin = io::stdin();
+    let mut stdout = io::stdout();
+    let mut buf = String::new();
+    stdin.read_to_string(&mut buf);
+    stdout.write_all(buf.as_bytes());
+    stdout.flush();
 }