README: keep usage copy

README.md

@@ -8,4 +8,36 @@ This interface lets you request real-time scheduling for one or more threads.
 
 ## Usage
 
-See the examples directory.
+```rust
+use nix::unistd::gettid;
+use std::thread;
+
+use rtkit_client_rs::{set_current_thread_priority, Error};
+
+fn main() {
+    println!("Main tid: {}", gettid());
+    thread::spawn(important_thread).join().unwrap();
+}
+
+fn important_thread() {
+    println!("Important thread tid: {}", gettid());
+
+    let requested_priority = 40;
+    let actual_priority = set_current_thread_priority(Some(requested_priority.try_into().unwrap()));
+    match actual_priority {
+        Ok(actual_priority) => println!("Requested priority: {requested_priority}, Actual priority: {}", actual_priority.value()),
+        Err(Error::PermissionDenied) => println!("Permission denied. Do you have polkit rules set up, or otherwise have the necessary permissions?"),
+        Err(e) => println!("Internal zbus error: {e}"),
+    }
+
+    let requested_nice_level = -10;
+    let actual_nice_level = rtkit_client_rs::set_current_thread_nice_level(Some(
+        requested_nice_level.try_into().unwrap(),
+    ));
+    match actual_nice_level {
+        Ok(actual_nice_level) => println!("Requested nice level: {requested_nice_level}, Actual nice level: {}", actual_nice_level.value()),
+        Err(Error::PermissionDenied) => println!("Permission denied. Do you have polkit rules set up, or otherwise have the necessary permissions?"),
+        Err(e) => println!("Internal zbus error: {e}"),
+    }
+}
+```