glibc/sysdeps/posix/cuserid.c

/* Copyright (C) 1991, 1996 Free Software Foundation, Inc.
This file is part of the GNU C Library.

The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.

The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
Library General Public License for more details.

You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB.  If
not, write to the Free Software Foundation, Inc., 675 Mass Ave,
Cambridge, MA 02139, USA.  */

#include <pwd.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>

/* Return the username of the caller.
   If S is not NULL, it points to a buffer of at least L_cuserid bytes
   into which the name is copied; otherwise, a static buffer is used.  */
char *
cuserid (s)
     char *s;
{
  static char name[L_cuserid];
  struct passwd *pwent = getpwuid (geteuid ());

  if (pwent == NULL)
    {
      if (s != NULL)
	s[0] = '\0';
      return NULL;
    }

  if (s == NULL)
    s = name;
  return strcpy (s, pwent->pw_name);
}