Use simpler example in readme

Author: vorner

README.md

@@ -39,91 +39,16 @@ each time).
 ```rust
 use std::io::Error;
 use std::sync::Arc;
-use std::sync::atomic::AtomicBool;
-
-use signal_hook::consts::signal::*;
-use signal_hook::consts::TERM_SIGNALS;
-use signal_hook::flag;
-// A friend of the Signals iterator, but can be customized by what we want yielded about each
-// signal.
-use signal_hook::iterator::SignalsInfo;
-use signal_hook::iterator::exfiltrator::WithOrigin;
-use signal_hook::low_level;
+use std::sync::atomic::{AtomicBool, Ordering};
 
 fn main() -> Result<(), Error> {
-    // Make sure double CTRL+C and similar kills
-    let term_now = Arc::new(AtomicBool::new(false));
-    for sig in TERM_SIGNALS {
-        // When terminated by a second term signal, exit with exit code 1.
-        // This will do nothing the first time (because term_now is false).
-        flag::register_conditional_shutdown(*sig, 1, Arc::clone(&term_now))?;
-        // But this will "arm" the above for the second time, by setting it to true.
-        // The order of registering these is important, if you put this one first, it will
-        // first arm and then terminate ‒ all in the first round.
-        flag::register(*sig, Arc::clone(&term_now))?;
-    }
-
-    // Subscribe to all these signals with information about where they come from. We use the
-    // extra info only for logging in this example (it is not available on all the OSes or at
-    // all the occasions anyway, it may return `Unknown`).
-    let mut sigs = vec![
-        // Some terminal handling
-        SIGTSTP, SIGCONT, SIGWINCH,
-        // Reload of configuration for daemons ‒ um, is this example for a TUI app or a daemon
-        // O:-)? You choose...
-        SIGHUP,
-        // Application-specific action, to print some statistics.
-        SIGUSR1,
-    ];
-    sigs.extend(TERM_SIGNALS);
-    let mut signals = SignalsInfo::<WithOrigin>::new(&sigs)?;
-
-    // This is the actual application that'll start in its own thread. We'll control it from
-    // this thread based on the signals, but it keeps running.
-    // This is called after all the signals got registered, to avoid the short race condition
-    // in the first registration of each signal in multi-threaded programs.
-    let app = App::run_background();
-
-    // Consume all the incoming signals. This happens in "normal" Rust thread, not in the
-    // signal handlers. This means that we are allowed to do whatever we like in here, without
-    // restrictions, but it also means the kernel believes the signal already got delivered, we
-    // handle them in delayed manner. This is in contrast with eg the above
-    // `register_conditional_shutdown` where the shutdown happens *inside* the handler.
-    let mut has_terminal = true;
-    for info in &mut signals {
-        // Will print info about signal + where it comes from.
-        eprintln!("Received a signal {:?}", info);
-        match info.signal {
-            SIGTSTP => {
-                // Restore the terminal to non-TUI mode
-                if has_terminal {
-                    app.restore_term();
-                    has_terminal = false;
-                    // And actually stop ourselves, by a little trick.
-                    low_level::raise(SIGSTOP)?;
-                }
-            }
-            SIGCONT => {
-                if !has_terminal {
-                    app.claim_term();
-                    has_terminal = true;
-                }
-            }
-            SIGWINCH => app.resize_term(),
-            SIGHUP => app.reload_config(),
-            SIGUSR1 => app.print_stats(),
-            term_sig => { // These are all the ones left
-                eprintln!("Terminating");
-                assert!(TERM_SIGNALS.contains(&term_sig));
-                break;
-            }
-        }
+    let term = Arc::new(AtomicBool::new(false));
+    signal_hook::flag::register(signal_hook::consts::SIGTERM, Arc::clone(&term))?;
+    while !term.load(Ordering::Relaxed) {
+        // Do some time-limited stuff here
+        // (if this could block forever, then there's no guarantee the signal will have any
+        // effect).
     }
-
-    // If during this another termination signal comes, the trick at the top would kick in and
-    // terminate early. But if it doesn't, the application shuts down gracefully.
-    app.wait_for_stop();
-
     Ok(())
 }
 ```