sysdeps/unix/getlogin_r.c

   1 /* Reentrant function to return the current login name.  Unix version.
   2    Copyright (C) 1991,92,96,97,98,2002,2010 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 Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the 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    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    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 #include "../login/utmp-private.h"
  29
  30 /* Return at most NAME_LEN characters of the login name of the user in NAME.
  31    If it cannot be determined or some other error occurred, return the error
  32    code.  Otherwise return 0.  */
  33
  34 #ifdef STATIC
  35 STATIC
  36 #endif
  37 int
  38 getlogin_r (name, name_len)
  39      char *name;
  40      size_t name_len;
  41 {
  42   char tty_pathname[2 + 2 * NAME_MAX];
  43   char *real_tty_path = tty_pathname;
  44   int result;
  45   struct utmp *ut, line, buffer;
  46
  47   /* Get name of tty connected to fd 0.  Return if not a tty or
  48      if fd 0 isn't open.  Note that a lot of documentation says that
  49      getlogin() is based on the controlling terminal---what they
  50      really mean is "the terminal connected to standard input".  The
  51      getlogin() implementation of DEC Unix, SunOS, Solaris, HP-UX all
  52      return NULL if fd 0 has been closed, so this is the compatible
  53      thing to do.  Note that ttyname(open("/dev/tty")) on those
  54      systems returns /dev/tty, so that is not a possible solution for
  55      getlogin().  */
  56
  57   result = __ttyname_r (0, real_tty_path, sizeof (tty_pathname));
  58
  59   if (result != 0)
  60     return result;
  61
  62   real_tty_path += 5;           /* Remove "/dev/".  */
  63   strncpy (line.ut_line, real_tty_path, sizeof line.ut_line);
  64
  65   /* We don't use the normal entry points __setutent et al, because we
  66      want setutent + getutline_r + endutent all to happen with the lock
  67      held so that our search is thread-safe.  */
  68
  69   __libc_lock_lock (__libc_utmp_lock);
  70   (*__libc_utmp_jump_table->setutent) ();
  71   result = (*__libc_utmp_jump_table->getutline_r) (&line, &buffer, &ut);
  72   if (result < 0)
  73     {
  74       if (errno == ESRCH)
  75         /* The caller expects ENOENT if nothing is found.  */
  76         result = ENOENT;
  77       else
  78         result = errno;
  79     }
  80   (*__libc_utmp_jump_table->endutent) ();
  81   __libc_utmp_jump_table = &__libc_utmp_unknown_functions;
  82   __libc_lock_unlock (__libc_utmp_lock);
  83
  84   if (result == 0)
  85     {
  86       size_t needed = strlen (ut->ut_user) + 1;
  87
  88       if (needed > name_len)
  89         {
  90           __set_errno (ERANGE);
  91           result = ERANGE;
  92         }
  93       else
  94         {
  95           memcpy (name, ut->ut_user, needed);
  96           result = 0;
  97         }
  98     }
  99
 100   return result;
 101 }
 102 #ifndef STATIC
 103 libc_hidden_def (getlogin_r)
 104 #endif