With POSIX IDs disabled, this function is equivalent to geteuid
    and returns the member number (in OpenVMS terms) from the user
    identification code (UIC).

    With POSIX IDs enabled, returns the real user ID.

    Format

      #include  <unistd.h>

      uid_t getuid  (void);

  Additional Information (explode) :

• Description
• Return Value