text: NAME
  getlogin, cuserid - get user name
  SYNOPSIS
  #include <unistd.h>
  char *getlogin(void);
  #include <stdio.h>
  char *cuserid(char *string);.
  cuserid returns a pointer to a string containing a user name user name. L_cuserid is
  declared in stdio.h.
  These functions let your program identify positively the user who is
  running (cuserid) or the user who logged in this session
  (getlogin). (These can differ when setuid programs are
  involved.)
  For most purposes, it is more useful to use the)
  CONFORMING TO
  POSIX.1. System V has a cuserid function which uses the real
  user ID rather than the effective user ID. The cuserid function
  was included in the 1988 version of POSIX, but removed from the 1990 version. purposes.
  Nobody knows precisely what cuserid() does - avoid it in portable programs -
  avoid it altogether - use getpwuid(geteuid()) instead, if that is
  what you meant.
  DO NOT USE cuserid().
  SEE ALSO
  geteuid(2),
  getuid(2)