sysdeps/unix/getlogin_r.c

   1 /* Reentrant function to return the current login name.  Unix version.
   2    Copyright (C) 1991, 1992, 1996, 1997, 1998 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Library General Public License as
   7    published by the Free Software Foundation; either version 2 of the
   8    License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Library General Public License for more details.
  14
  15    You should have received a copy of the GNU Library General Public
  16    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  17    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  18    Boston, MA 02111-1307, USA.  */
  19
  20 #include <errno.h>
  21 #include <unistd.h>
  22 #include <string.h>
  23 #include <stdio.h>
  24 #include <limits.h>
  25 #include <fcntl.h>
  26
  27 #include <utmp.h>
  28
  29 /* Return at most NAME_LEN characters of the login name of the user in NAME.
  30    If it cannot be determined or some other error occurred, return the error
  31    code.  Otherwise return 0.  */
  32
  33 int
  34 getlogin_r (name, name_len)
  35      char *name;
  36      size_t name_len;
  37 {
  38   char tty_pathname[2 + 2 * NAME_MAX];
  39   char *real_tty_path = tty_pathname;
  40   int result = 0;
  41   struct utmp *ut, line, buffer;
  42
  43   /* Get name of tty connected to fd 0.  Return if not a tty or
  44      if fd 0 isn't open.  Note that a lot of documentation says that
  45      getlogin() is based on the controlling terminal---what they
  46      really mean is "the terminal connected to standard input".  The
  47      getlogin() implementation of DEC Unix, SunOS, Solaris, HP-UX all
  48      return NULL if fd 0 has been closed, so this is the compatible
  49      thing to do.  Note that ttyname(open("/dev/tty")) on those
  50      systems returns /dev/tty, so that is not a possible solution for
  51      getlogin().  */
  52
  53   result = __ttyname_r (0, real_tty_path, sizeof (tty_pathname));
  54
  55   if (result != 0)
  56     return result;
  57
  58   real_tty_path += 5;           /* Remove "/dev/".  */
  59
  60   __setutent ();
  61   strncpy (line.ut_line, real_tty_path, sizeof line.ut_line);
  62   if (__getutline_r (&line, &buffer, &ut) < 0)
  63     {
  64       if (errno == ESRCH)
  65         /* The caller expects ENOENT if nothing is found.  */
  66         result = ENOENT;
  67       else
  68         result = errno;
  69     }
  70   else
  71     {
  72       size_t needed = strlen (ut->ut_user) + 1;
  73
  74       if (needed > name_len)
  75         {
  76           __set_errno (ERANGE);
  77           result = ERANGE;
  78         }
  79       else
  80         {
  81           memcpy (name, ut->ut_user, needed);
  82           result = 0;
  83         }
  84     }
  85   __endutent ();
  86
  87   return result;
  88 }