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.
There are also a bunch of proposed 2025H1 goals. Depending on how things pan out, 2025H1 might have us see not only Rust 2024 edition, but also the new trait solver ready for general use, and new borrowchecker on nightly.