sysdeps/posix/ttyname.c

   1 /* Copyright (C) 1991-2015 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 (fd, mydev, myino, save, dostat)
  39      int fd;
  40      dev_t mydev;
  41      ino_t myino;
  42      int save;
  43      int *dostat;
  44 {
  45   static const char dev[] = "/dev";
  46   static size_t namelen;
  47   struct stat st;
  48   DIR *dirstream;
  49   struct dirent *d;
  50
  51   dirstream = __opendir (dev);
  52   if (dirstream == NULL)
  53     {
  54       *dostat = -1;
  55       return NULL;
  56     }
  57
  58   while ((d = __readdir (dirstream)) != NULL)
  59     if (((ino_t) d->d_fileno == myino || *dostat)
  60         && strcmp (d->d_name, "stdin")
  61         && strcmp (d->d_name, "stdout")
  62         && strcmp (d->d_name, "stderr"))
  63       {
  64         size_t dlen = _D_ALLOC_NAMLEN (d);
  65         if (sizeof (dev) + dlen > namelen)
  66           {
  67             free (getttyname_name);
  68             namelen = 2 * (sizeof (dev) + dlen); /* Big enough.  */
  69             getttyname_name = malloc (namelen);
  70             if (! getttyname_name)
  71               {
  72                 *dostat = -1;
  73                 /* Perhaps it helps to free the directory stream buffer.  */
  74                 (void) __closedir (dirstream);
  75                 return NULL;
  76               }
  77             *((char *) __mempcpy (getttyname_name, dev, sizeof (dev) - 1))
  78               = '/';
  79           }
  80         (void) __mempcpy (&getttyname_name[sizeof (dev)], d->d_name, dlen);
  81         if (stat (getttyname_name, &st) == 0
  82 #ifdef _STATBUF_ST_RDEV
  83             && S_ISCHR (st.st_mode) && st.st_rdev == mydev
  84 #else
  85             && (ino_t) d->d_fileno == myino && st.st_dev == mydev
  86 #endif
  87            )
  88           {
  89             (void) __closedir (dirstream);
  90             __ttyname = getttyname_name;
  91             __set_errno (save);
  92             return getttyname_name;
  93           }
  94       }
  95
  96   (void) __closedir (dirstream);
  97   __set_errno (save);
  98   return NULL;
  99 }
 100
 101 /* Return the pathname of the terminal FD is open on, or NULL on errors.
 102    The returned storage is good only until the next call to this function.  */
 103 char *
 104 ttyname (fd)
 105      int fd;
 106 {
 107   struct stat st;
 108   int dostat = 0;
 109   char *name;
 110   int save = errno;
 111
 112   if (!__isatty (fd))
 113     return NULL;
 114
 115   if (fstat (fd, &st) < 0)
 116     return NULL;
 117
 118 #ifdef _STATBUF_ST_RDEV
 119   name = getttyname (fd, st.st_rdev, st.st_ino, save, &dostat);
 120 #else
 121   name = getttyname (fd, st.st_dev, st.st_ino, save, &dostat);
 122 #endif
 123
 124   if (!name && dostat != -1)
 125     {
 126       dostat = 1;
 127 #ifdef _STATBUF_ST_RDEV
 128       name = getttyname (fd, st.st_rdev, st.st_ino, save, &dostat);
 129 #else
 130       name = getttyname (fd, st.st_dev, st.st_ino, save, &dostat);
 131 #endif
 132     }
 133
 134   return name;
 135 }