VMS Help CC, Run-time functions, getuid  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  Returns, in OpenVMS terms, the member number from the user
  identification code (UIC).  For example, if the UIC is [313,031],
  313 is the member number.

  Syntax:

       #include <unistd.h>

       uid_t getuid(void);