function main returns exit status

bin/src/main.rs

@@ -71,10 +71,18 @@
     BeginNewMain(UpgradeError),
     #[error("{0}")]
     Cli(CtlError),
+    #[error("paw io error: {0}")]
+    Io(std::io::Error),
+}
+
+impl From<std::io::Error> for MainError {
+    fn from(value: std::io::Error) -> Self {
+        Self::Io(value)
+    }
 }
 
 #[paw::main]
-fn main(args: Args) {
+fn main(args: Args) -> Result<(), MainError> {
     register_panic_hook();
 
     let result = match args.cmd {
@@ -119,10 +127,11 @@
         }
         _ => ctl::ctl(args).map_err(MainError::Cli),
     };
-    match result {
-        Ok(_) => {}
-        Err(main_error) => println!("{}", main_error),
+
+    if let Err(main_error) = &result {
+        eprintln!("\n{main_error}\n");
     }
+    result
 }
 
 /// Set workers process affinity, see man sched_setaffinity
@@ -130,7 +139,7 @@
 /// Can bind multiple processes to a CPU core if there are more processes
 /// than CPU cores. Only works on Linux.
 #[cfg(target_os = "linux")]
 fn set_workers_affinity(workers: &Vec<WorkerSession>) {
     let mut cpu_count = 0;
     let max_cpu = num_cpus::get();
 
@@ -169,7 +178,7 @@
 #[cfg(target_os = "linux")]
 use std::mem;
 #[cfg(target_os = "linux")]
 fn set_process_affinity(pid: pid_t, cpu: usize) {
     unsafe {
         let mut cpu_set: cpu_set_t = mem::zeroed();
         let size_cpu_set = mem::size_of::<cpu_set_t>();