How to get the error why a process fails to spawn?

help
1

Using the std::process::Command's .spawn() method, I get a Result with an error when it fails.

But how do I get the error code of why it failed?

I just getting an error struct. When I print, it contains the information I need (like the error code, a descriptive message, kind), but I can't get it in the code. Of course, parsing the string of an error that may totally change just to get the error code is absolutely stupid, error-prone, fragile, and a non-go.

But I can't find how to get the error code. How to do it?

2

The spawn method from std::process::Command returns a Result<Child, std::io::Error>. You can get the ErrorKind enum like this:

match Command::new("ls").spawn() {
  Ok(output) => // Do something with the output
  Err(error) => match error.kind() {
    // Here you'll match the variants from https://doc.rust-lang.org/std/io/enum.ErrorKind.html
  }
}
2 Likes
3

Thanks! That's exactly what I need.

I think I should improve a lot my skills in reading the rust documentation. Sometimes it can be a little dry, but usually, the answer is there and I fail to see it.

4

I agree that it can take some time to get used to Rust's documentation. If you have any observations / ideas on how to improve any section in particular (i.e. how to make it easier for users to find how to match the specific error from std::io::Error), I think they would be very welcomed.

At the same time, IMHO the Rust documentation is by far the best one I have seen / used in my career. I can easily navigate docs from a specific crate to the standard library and go back and forth until I get the whole picture of how to work with it. The experience is much better than traditional isolated documentation sites for each one of my dependencies.

5

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