feat(main): prevent multiple instances using file lock

Introduce a file lock mechanism to ensure only one instance of the
application runs at a time. This prevents resource contention and
duplicate updates to SketchyBar.

Author: joncrangle

Cargo.lock

@@ -1,16 +1,17 @@
 [package]
 name = "stats_provider"
-version = "0.8.0"
+version = "0.8.1"
 description = "A simple system stats event provider for Sketchybar."
 edition = "2021"
 build = "build.rs"
 
 [dependencies]
 anyhow = "1.0.100"
 clap = { version = "4.5.54", features = ["derive"] }
+fs2 = "0.4.3"
 starship-battery = "0.10.3"
 sysinfo = { version = "0.37.2", default-features = false, features = ["component", "disk", "network", "system"] }
 tokio = { version = "1", features = ["full"] }
 
 [build-dependencies]
-cc = "1.2.51"
+cc = "1.2.52"

Cargo.toml

@@ -2,7 +2,10 @@ mod cli;
 mod sketchybar;
 mod stats;
 
+use std::fs::File;
+
 use anyhow::{Context, Result};
+use fs2::FileExt;
 use sketchybar::Sketchybar;
 use stats::{
     get_battery_stats, get_cpu_stats, get_disk_stats, get_memory_stats, get_network_stats,
@@ -255,9 +258,20 @@ async fn collect_stats_commands(
     Ok(updated_tick)
 }
 
+fn acquire_lock() -> Option<File> {
+    let file = File::create("/tmp/stats_provider.lock").ok()?;
+    file.try_lock_exclusive().ok()?;
+    Some(file)
+}
+
 #[cfg(target_os = "macos")]
 #[tokio::main]
 async fn main() -> Result<()> {
+    let _lock = match acquire_lock() {
+        Some(lock) => lock,
+        None => return Ok(()),
+    };
+
     let cli = cli::parse_args();
 
     cli::validate_cli(&cli).context("Invalid CLI arguments")?;