Errors and termination

Failure as a value

A possibly absent value is Option.Some(value) or Option.None. A fallible operation returns Result.Ok(value) or Result.Err(error). Handle each case with match. ? extracts success or propagates an error to the caller; the function needs a compatible Result return type.

Termination

panic(message) terminates the program. Panic and runtime errors skip normal block cleanup. Handle expected file and input errors using Result. Exceptions are unavailable.

CLI exit status	Meaning
0	Success
1	Code, runtime, or test error, or no matching tests
2	Invalid command usage

run propagates the program’s exit status.

Learn more: Missing values and errors · Command-line tools