sysdeps/posix/ttyname_r.c

   1 /* Copyright (C) 1991, 92, 93, 95, 96 Free Software Foundation, Inc.
   2 This file is part of the GNU C Library.
   3
   4 The GNU C Library is free software; you can redistribute it and/or
   5 modify it under the terms of the GNU Library General Public License as
   6 published by the Free Software Foundation; either version 2 of the
   7 License, or (at your option) any later version.
   8
   9 The GNU C Library is distributed in the hope that it will be useful,
  10 but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12 Library General Public License for more details.
  13
  14 You should have received a copy of the GNU Library General Public
  15 License along with the GNU C Library; see the file COPYING.LIB.  If
  16 not, write to the Free Software Foundation, Inc., 675 Mass Ave,
  17 Cambridge, MA 02139, USA.  */
  18
  19 #include <errno.h>
  20 #include <limits.h>
  21 #include <stddef.h>
  22 #include <dirent.h>
  23 #include <sys/types.h>
  24 #include <sys/stat.h>
  25 #include <unistd.h>
  26 #include <string.h>
  27 #include <stdlib.h>
  28
  29 #ifndef MIN
  30 # define MIN(a, b) ((a) < (b) ? (a) : (b))
  31 #endif
  32
  33 /* Store at most BUFLEN character of the pathname of the terminal FD is
  34    open on in BUF.  Return 0 on success, -1 otherwise.  */
  35 int
  36 __ttyname_r (fd, buf, buflen)
  37      int fd;
  38      char *buf;
  39      int buflen;
  40 {
  41   static const char dev[] = "/dev";
  42   struct stat st;
  43   dev_t mydev;
  44   ino_t myino;
  45   DIR *dirstream;
  46   struct dirent *d;
  47   int save = errno;
  48
  49   /* Test for the absolute minimal size.  This makes life easier inside
  50      the loop.  */
  51   if (buflen < (int) (sizeof (dev) + 1))
  52     {
  53       __set_errno (EINVAL);
  54       return -1;
  55     }
  56
  57   if (!__isatty (fd))
  58     return -1;
  59
  60   if (fstat (fd, &st) < 0)
  61     return -1;
  62   mydev = st.st_dev;
  63   myino = st.st_ino;
  64
  65   dirstream = opendir (dev);
  66   if (dirstream == NULL)
  67     return -1;
  68
  69   /* Prepare the result buffer.  */
  70   memcpy (buf, dev, sizeof (dev) - 1);
  71   buf[sizeof (dev) - 1] = '/';
  72   buflen -= sizeof (dev);
  73
  74   while ((d = readdir (dirstream)) != NULL)
  75     if (d->d_fileno == myino)
  76       {
  77         char *cp;
  78
  79         cp = __stpncpy (&buf[sizeof (dev)], d->d_name,
  80                         MIN ((int) (_D_EXACT_NAMLEN (d) + 1), buflen));
  81         cp[0] = '\0';
  82
  83         if (stat (buf, &st) == 0 && st.st_dev == mydev)
  84           {
  85             (void) closedir (dirstream);
  86             __set_errno (save);
  87             return 0;
  88           }
  89       }
  90
  91   (void) closedir (dirstream);
  92   __set_errno (save);
  93   return -1;
  94 }
  95 weak_alias (__ttyname_r, ttyname_r)