ctermid gets the path of the controlling terminal, see [ctermid](https://pubs.opengroup.org/onlinepubs/9699919799/functions/ctermid.html): ```rust pub fn ctermid(c: *mut libc::c_char) -> *mut libc::c_char; ``` This is POSIX API; it definitely exists on Linux, and I presume on all other Unix systems as well.
