title: How to determine the effective user id of a process in Rust?
body: <p>On Linux and other POSIX systems, a program can be executed under the identity of another user (i.e. <code>euid</code>). Normally, you'd call <code>geteuid</code> and friends to reliably determine the current identities of the process. However, I couldn't figure out a reliable way to determine these identities using only  rust's standard library. </p>
  
  <p>The only thing I found that was close is <code>std::os::unix::MetadataExt</code>.</p>
  
  <p>Is it currently possible to determine the <code>euid</code> (and other ids) of process using the rust's standard library? Is there a function or trait I'm missing?</p>