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 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   {
  44     int err;
  45     int d = __open ("/dev/tty", 0);
  46     if (d < 0)
  47       return errno;
  48
  49     result = ttyname_r (d, real_tty_path, sizeof (tty_pathname));
  50     err = errno;
  51     (void) close (d);
  52
  53     if (result < 0)
  54       {
  55         __set_errno (err);
  56         return err;
  57       }
  58   }
  59
  60   real_tty_path += 5;           /* Remove "/dev/".  */
  61
  62   __setutent ();
  63   strncpy (line.ut_line, real_tty_path, sizeof line.ut_line);
  64   if (__getutline_r (&line, &buffer, &ut) < 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       size_t needed = strlen (ut->ut_line) + 1;
  75
  76       if (needed < name_len)
  77         {
  78           __set_errno (ERANGE);
  79           result = ERANGE;
  80         }
  81       else
  82         {
  83           memcpy (name, ut->ut_line, needed);
  84           result = 0;
  85         }
  86     }
  87   __endutent ();
  88
  89   return result;
  90 }