From: Carl Worth <cworth@cworth.org>
Date: Tue, 10 Mar 2026 01:52:58 +0000 (-0700)
Subject: Return an actual value from main
X-Git-Url: https://git.cworth.org/git?a=commitdiff_plain;h=45b4fb4058591995c405572f8921086b79325077;p=rust-learning

Return an actual value from main

This is a more idiomatic behavior from main, using a Result to return
either the unit type (which will cause a return of 0) or else an Error
(coerced from a string by using .into()). In that case, the program
will print "Error: " and our error string before exiting with a value
of 1.
---

diff --git a/src/main.rs b/src/main.rs
index 34e2214..404dde8 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,7 +1,10 @@
-fn main() {
+use std::error::Error;
+
+fn main() -> Result<(), Box<dyn Error>> {
     let args: Vec<String> = std::env::args().collect();
     if args.len() < 2 {
-        eprintln!("Usage: {} <race-config.json>", args[0]);
-        std::process::exit(1);
+        return Err(format!("Usage: {} <race-config.json>", args[0]).into());
     }
+
+    Ok(())
 }