Why does Rust not have a return value in the main function, and how to return a value anyway?

Question

In Rust the main function is defined like this:

fn main() {

}

This function does not allow for a return value though. Why would a language not

Answer 1

std::process::exit(code: i32) is the way to exit with a code.

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Rust does it this way so that there is a consistent explicit interface for returning a value from a program, wherever it is set from. If main starts a series of tasks then any of these can set the return value, even if main has exited.

Rust does have a way to write a main function that returns a value, however it is normally abstracted within stdlib. See the documentation on writing an executable without stdlib for details.