sysdeps/posix/ttyname.c

   1 /* Copyright (C) 1991-2016 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 Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the 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    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, see
  16    <http://www.gnu.org/licenses/>.  */
  17
  18 #include <errno.h>
  19 #include <limits.h>
  20 #include <stddef.h>
  21 #include <dirent.h>
  22 #include <sys/types.h>
  23 #include <sys/stat.h>
  24 #include <unistd.h>
  25 #include <string.h>
  26 #include <stdlib.h>
  27
  28 char *__ttyname;
  29
  30 static char *getttyname (int fd, dev_t mydev, ino_t myino,
  31                          int save, int *dostat) internal_function;
  32
  33
  34 libc_freeres_ptr (static char *getttyname_name);
  35
  36 static char *
  37 internal_function
  38 getttyname (int fd, dev_t mydev, ino_t myino, int save, int *dostat)
  39 {
  40   static const char dev[] = "/dev";
  41   static size_t namelen;
  42   struct stat st;
  43   DIR *dirstream;
  44   struct dirent *d;
  45
  46   dirstream = __opendir (dev);
  47   if (dirstream == NULL)
  48     {
  49       *dostat = -1;
  50       return NULL;
  51     }
  52
  53   while ((d = __readdir (dirstream)) != NULL)
  54     if (((ino_t) d->d_fileno == myino || *dostat)
  55         && strcmp (d->d_name, "stdin")
  56         && strcmp (d->d_name, "stdout")
  57         && strcmp (d->d_name, "stderr"))
  58       {
  59         size_t dlen = _D_ALLOC_NAMLEN (d);
  60         if (sizeof (dev) + dlen > namelen)
  61           {
  62             free (getttyname_name);
  63             namelen = 2 * (sizeof (dev) + dlen); /* Big enough.  */
  64             getttyname_name = malloc (namelen);
  65             if (! getttyname_name)
  66               {
  67                 *dostat = -1;
  68                 /* Perhaps it helps to free the directory stream buffer.  */
  69                 (void) __closedir (dirstream);
  70                 return NULL;
  71               }
  72             *((char *) __mempcpy (getttyname_name, dev, sizeof (dev) - 1))
  73               = '/';
  74           }
  75         (void) __mempcpy (&getttyname_name[sizeof (dev)], d->d_name, dlen);
  76         if (stat (getttyname_name, &st) == 0
  77 #ifdef _STATBUF_ST_RDEV
  78             && S_ISCHR (st.st_mode) && st.st_rdev == mydev
  79 #else
  80             && (ino_t) d->d_fileno == myino && st.st_dev == mydev
  81 #endif
  82            )
  83           {
  84             (void) __closedir (dirstream);
  85             __ttyname = getttyname_name;
  86             __set_errno (save);
  87             return getttyname_name;
  88           }
  89       }
  90
  91   (void) __closedir (dirstream);
  92   __set_errno (save);
  93   return NULL;
  94 }
  95
  96 /* Return the pathname of the terminal FD is open on, or NULL on errors.
  97    The returned storage is good only until the next call to this function.  */
  98 char *
  99 ttyname (int fd)
 100 {
 101   struct stat st;
 102   int dostat = 0;
 103   char *name;
 104   int save = errno;
 105
 106   if (!__isatty (fd))
 107     return NULL;
 108
 109   if (fstat (fd, &st) < 0)
 110     return NULL;
 111
 112 #ifdef _STATBUF_ST_RDEV
 113   name = getttyname (fd, st.st_rdev, st.st_ino, save, &dostat);
 114 #else
 115   name = getttyname (fd, st.st_dev, st.st_ino, save, &dostat);
 116 #endif
 117
 118   if (!name && dostat != -1)
 119     {
 120       dostat = 1;
 121 #ifdef _STATBUF_ST_RDEV
 122       name = getttyname (fd, st.st_rdev, st.st_ino, save, &dostat);
 123 #else
 124       name = getttyname (fd, st.st_dev, st.st_ino, save, &dostat);
 125 #endif
 126     }
 127
 128   return name;
 129 }