Fix booted to work as expected when systemd is not running

CHANGELOG.md

@@ -9,6 +9,8 @@
  - the MSRV is now defined as 1.82
 
  ### Fixed
+
+ - fixed `booted` to return `Ok(false)` when not running under systemd
  - fixed `watchdog_enabled` to handle missing `WATCHDOG_PID`
 
 ## [0.4.5] - 2025-01-18

src/lib.rs

@@ -131,11 +131,18 @@ impl NotifyState<'_> {
 /// # Example
 ///
 /// ```no_run
-/// let _ = sd_notify::booted();
+/// match sd_notify::booted() {
+///     Ok(true) => { println!("System is booted under systemd")},
+///     Ok(false) => { println!("System is not booted under systemd")},
+///     Err(e) => { println!("Error: {}", e)},
+/// }
 /// ```
 pub fn booted() -> io::Result<bool> {
-    let m = fs::symlink_metadata("/run/systemd/system")?;
-    Ok(m.is_dir())
+    match fs::symlink_metadata("/run/systemd/system") {
+        Ok(m) => Ok(m.is_dir()),
+        Err(e) if matches!(e.kind(), ErrorKind::NotFound) => Ok(false),
+        Err(e) => Err(e),
+    }
 }
 
 // Constants for env variable names so that we don't typo them.