I need to get the name of the user that is running the current process (on Linux) but I can't find anything in the std lib for that which kinda surprises me.
I've found function to set the UID but nothing to retrieve it so let alone retrieving the user's name.
What am I missing here?
Thanks!
Rust's std is intentionally a minimal library rather than a "kitchen sink and everything else" library. Users are expected to import functionality from the crates.io ecosystem. There are a number of reasons for this choice that have been documented repeatedly in this forum—hence forum search is strongly suggested.
Those reasons include two facts:
items needing special compiler support must be in std, which then requires that std be maintained directly by the already-overburdened compiler team. (That's why each version of std is only compatible with the identical version of rustc.)
Rust's semver past-and-future compatibility guarantees for std preclude any kind of breaking-change improvements
Other crates in the crates.io ecosystem do not suffer from these limitations, so by design they are intended to be the "go to" place for most functionality that doesn't require special support within the compiler.
I understand that 
But I was surprise to have the PID available and not the current user. The users crate relies on libc to achieve this which is a pity.
User ids work differently between operating systems. For Unix there are the real user id, effective user id and stored user id which are integers. For Windows there is the user security identifier (SID) which is a string like S-1-5-21-1-2-3-513 (example taken from https://docs.microsoft.com/en-us/openspecs/windows_protocols/ms-dtyp/81d92bba-d22b-4a8c-908a-554ab29148ab) For Fuchsia I am not even sure if such a concept as "user" exists. The L4 family of kernels doesn't have users. Instead it uses capabilities for access control.