sysdeps/posix/ttyname.c

   1 /* Copyright (C) 1991, 1992, 1993 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 <ansidecl.h>
  20 #include <errno.h>
  21 #include <limits.h>
  22 #include <stddef.h>
  23 #include <dirent.h>
  24 #include <sys/types.h>
  25 #include <sys/stat.h>
  26 #include <unistd.h>
  27 #include <string.h>
  28 #include <stdlib.h>
  29
  30 char *__ttyname = NULL;
  31
  32 /* Return the pathname of the terminal FD is open on, or NULL on errors.
  33    The returned storage is good only until the next call to this function.  */
  34 char *
  35 DEFUN(ttyname, (fd), int fd)
  36 {
  37   static CONST char dev[] = "/dev";
  38   static char *name;
  39   static size_t namelen = 0;
  40   struct stat st;
  41   dev_t mydev;
  42   ino_t myino;
  43   DIR *dirstream;
  44   struct dirent *d;
  45   int save = errno;
  46
  47   if (fstat (fd, &st) < 0)
  48     return NULL;
  49   mydev = st.st_dev;
  50   myino = st.st_ino;
  51
  52   dirstream = opendir (dev);
  53   if (dirstream == NULL)
  54     return NULL;
  55
  56   while ((d = readdir (dirstream)) != NULL)
  57     if (d->d_fileno == myino)
  58       {
  59         if (sizeof (dev) + d->d_namlen + 1 > namelen)
  60           {
  61             free (name);
  62             namelen = 2 * (sizeof (dev) + d->d_namlen + 1); /* Big enough.  */
  63             name = malloc (namelen);
  64             if (! name)
  65               return NULL;
  66             (void) memcpy (name, dev, sizeof (dev) - 1);
  67             name[sizeof (dev) - 1] = '/';
  68           }
  69         (void) memcpy (&name[sizeof (dev)], d->d_name, d->d_namlen + 1);
  70         if (stat (name, &st) == 0 && st.st_dev == mydev)
  71           {
  72             (void) closedir (dirstream);
  73             __ttyname = name;
  74             errno = save;
  75             return name;
  76           }
  77       }
  78
  79   (void) closedir (dirstream);
  80   errno = save;
  81   return NULL;
  82 }