Store alarm_exec as Option<T>.

src/alarm.rs

@@ -262,13 +262,13 @@ pub fn alarm_exec(config: &Config, elapsed: u32) {
         time = format!("{:02}:{:02}:{:02}", elapsed /3600, (elapsed / 60) % 60, elapsed % 60);
     }
 
+    if let Some(exec) = &config.alarm_exec {
         // Replace every occurrence of "%s".
-    for s in config.alarm_exec.iter() {
+        for s in exec {
             args.push(s.replace("%s", &time));
         }
 
-    if Command::new(
-        &config.alarm_exec[0])
+        if Command::new(&exec[0])
             .args(&args[1..])
             .stdout(Stdio::null())
             .stdin(Stdio::null())
@@ -277,4 +277,5 @@ pub fn alarm_exec(config: &Config, elapsed: u32) {
             eprintln!("Error: Could not execute command");
         }
     }
+}
 

src/main.rs

@@ -32,14 +32,14 @@ const MENUBAR_SHORT: &str =
 
 pub struct Config {
     plain: bool,
-    alarm_exec: Vec<String>,
+    alarm_exec: Option<Vec<String>>,
 }
 
 
 fn main() {
     let mut config = Config {
         plain: false,
-        alarm_exec: Vec::new(),
+        alarm_exec: None,
     };
     parse_args(&mut config);
 
@@ -179,7 +179,8 @@ fn main() {
                 write!(stdout, "{}", 0x07 as char).unwrap();
                 layout.force_redraw = true;
 
-                if config.alarm_exec.len() > 0 {
+                // Run command if configured.
+                if config.alarm_exec.is_some() {
                     alarm_exec(&config, clock.elapsed);
                 }
             }
@@ -254,10 +255,11 @@ fn parse_args(config: &mut Config) {
                 // Find position of this flag.
                 let i = env::args().position(|s| { s == "-e" || s == "--exec" }).unwrap();
                 // Copy everything thereafter.
-                config.alarm_exec = env::args().skip(i + 1).collect();
-                if config.alarm_exec.len() == 0 {
+                let exec: Vec<String> = env::args().skip(i + 1).collect();
+                if exec.len() == 0 {
                     usage();
                 } else {
+                    config.alarm_exec = Some(exec);
                     // Ignore everything after this flag.
                     break;
                 }