add pty example that runs whoami

Refs: #27

pty/examples/whoami.rs

@@ -0,0 +1,26 @@
+use portable_pty::{CommandBuilder, PtySize, PtySystemSelection};
+
+fn main() {
+    let pty_system = PtySystemSelection::default().get().unwrap();
+
+    let (master, slave) = pty_system
+        .openpty(PtySize {
+            rows: 24,
+            cols: 80,
+            pixel_width: 0,
+            pixel_height: 0,
+        })
+        .unwrap();
+
+    let cmd = CommandBuilder::new("whoami");
+    let mut child = slave.spawn_command(cmd).unwrap();
+
+    let mut s = String::new();
+    master
+        .try_clone_reader()
+        .unwrap()
+        .read_to_string(&mut s)
+        .unwrap();
+    println!("output: {}", s);
+    child.wait().unwrap();
+}