I was reading bytecodealliance/rustix#100 (comment) and remembered that Rust's std doesn't have a way to pass (non-stdio) file descriptors to child processes.

I was wondering, could a way to do that be added into std::command::Command?

I also propose these properties:

• Know the FD numbers before spawning, e.g. for the LISTEN_FDS environment variable. Maybe the user provides the FD numbers and the library uses dup2?
• close_fds=True (is this applicable? not sure how it's implemented in Python)

Prior work:

• cap_std_ext::CapStdExtCommandExt
• std::process::Command and I/O safety bytecodealliance/rustix#100
• @sunfishcode @cgwalters