Need some help in understanding how to read some parts of library pages (std::process)
Need some help in understanding how to read some parts of library pages (std::process)
I am trying to understand the std::process::Termination trait.
As I'm not really used to read libraries, I took this as a challenge to try understanding a bit more about how to read them as well.
I think trying to build a library would give me better understanding, but for now...
Termination is quite easy, from the trait page I can see that this trait has single method: report, which returns an ExitCode.
pub trait Termination {
fn report(self) -> ExitCode;
}
But when I try to dig in further and i read the page related to ExitCode, it confuses me a bit.
ExitCode is a struct, therefore it behaves like a type with many fields which define the types contained in the struct.
I cannot really understand what's the point of this type.. I don't see any fields defined in the struct and this part confuses me a lot:
The standard library provides the canonical SUCCESS and FAILURE exit codes as well as From<u8> for ExitCode for constructing other arbitrary exit codes.
I even thought this meant it was an enum which had the SUCCESS, FAILURE etc as variants, but this does not seem the case.
Can you help me to understand how this specific structs work, what exactly does it do and how I should read library pages like this one?
In addition to the other comment about the exit code, you might be interested in the exitcode crate, which offers up a BSD convention for those exit codes.
They are, essentially, just numbers on unixes and don't really have as much standardization as e.g. HTTP codes afaik. Various programs may have their own local conventions as to what an exit code means.
ExitCodeis a struct, therefore it behaves like a type with many fields which define the types contained in the struct.That's a bit too off.
structs in rust are product types. A struct may define zero or more fields. And fields can be named or not. if not, such structs are called tuple structs.In the doc page, if you clicked on source, it would have taken you to the definition.
pub struct ExitCode(imp::ExitCode);That's a public struct with one unnamed private field. The type of the private field also happens to be private/internal.
As for why, usually the purpose is providing type safety, a unified interface,... etc. Notice how for example a windows-only extension trait is implemented that allows converting raw u32 exit codes into
ExitCode.So now you have exit codes possibly sourced from u8 or u32 values depending on the platform. And you need a safe unified interface to represent them.
I hope that's an enough starting point.
Here's the source of the
ExitCodeimplementation for Unix: https://doc.rust-lang.org/src/std/sys/pal/unix/process/process_common.rs.html#622I'm a seasoned Rust dev and this wasn't easy for me to find. The std lib can be somewhat complex, because it needs to cover all possible use-cases...