sysdeps/unix/getlogin_r.c

   1 /* Reentrant function to return the current login name.  Unix version.
   2 Copyright (C) 1991, 1992, 1996 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
  17 not, write to the Free Software Foundation, Inc., 675 Mass Ave,
  18 Cambridge, MA 02139, 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 occured, 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_data utmp_data;
  42   struct utmp *ut;
  43
  44   {
  45     int err;
  46     int d = __open ("/dev/tty", 0);
  47     if (d < 0)
  48       return errno;
  49
  50     result = ttyname_r (d, real_tty_path, sizeof (tty_pathname));
  51     err = errno;
  52     (void) close (d);
  53
  54     if (result < 0)
  55       {
  56         errno = err;
  57         return err;
  58       }
  59   }
  60
  61   real_tty_path += 5;           /* Remove "/dev/".  */
  62
  63   setutent_r (&utmp_data);
  64   if (getutline_r (real_tty_path, &ut, &utmp_data) < 0)
  65     {
  66       if (errno == ESRCH)
  67         /* The caller expects ENOENT if nothing is found.  */
  68         result = ENOENT;
  69       else
  70         result = errno;
  71     }
  72   else
  73     {
  74       strncpy (name, ut->ut_line, name_len);
  75       result = 0;
  76     }
  77   endutent_r (&utmp_data);
  78
  79   return result;
  80 }