sysdeps/posix/ttyname_r.c

   1 /* Copyright (C) 1991-2024 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    <https://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 #ifndef MIN
  29 # define MIN(a, b) ((a) < (b) ? (a) : (b))
  30 #endif
  31
  32 static const char dev[] = "/dev";
  33
  34 static int getttyname_r (int fd, char *buf, size_t buflen,
  35                          dev_t mydev, ino_t myino, int save,
  36                          int *dostat) __THROW;
  37
  38 static int
  39 getttyname_r (int fd, char *buf, size_t buflen, dev_t mydev, ino_t myino,
  40               int save, int *dostat)
  41 {
  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 errno;
  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         char *cp;
  60         size_t needed = _D_EXACT_NAMLEN (d) + 1;
  61
  62         if (needed > buflen)
  63           {
  64             *dostat = -1;
  65             (void) __closedir (dirstream);
  66             __set_errno (ERANGE);
  67             return ERANGE;
  68           }
  69
  70         cp = __stpncpy (&buf[sizeof (dev)], d->d_name, needed);
  71         cp[0] = '\0';
  72
  73         if (stat (buf, &st) == 0
  74 #ifdef _STATBUF_ST_RDEV
  75             && S_ISCHR (st.st_mode) && st.st_rdev == mydev
  76 #else
  77             && (ino_t) d->d_fileno == myino && st.st_dev == mydev
  78 #endif
  79            )
  80           {
  81             (void) __closedir (dirstream);
  82             __set_errno (save);
  83             return 0;
  84           }
  85       }
  86
  87   (void) __closedir (dirstream);
  88   __set_errno (save);
  89   /* It is not clear what to return in this case.  `isatty' says FD
  90      refers to a TTY but no entry in /dev has this inode.  */
  91   return ENOTTY;
  92 }
  93
  94 /* Store at most BUFLEN character of the pathname of the terminal FD is
  95    open on in BUF.  Return 0 on success,  otherwise an error number.  */
  96 int
  97 __ttyname_r (int fd, char *buf, size_t buflen)
  98 {
  99   struct stat st;
 100   int dostat = 0;
 101   int save = errno;
 102   int ret;
 103
 104   /* Test for the absolute minimal size.  This makes life easier inside
 105      the loop.  */
 106   if (!buf)
 107     {
 108       __set_errno (EINVAL);
 109       return EINVAL;
 110     }
 111
 112   if (buflen < (int) (sizeof (dev) + 1))
 113     {
 114       __set_errno (ERANGE);
 115       return ERANGE;
 116     }
 117
 118   if (!__isatty (fd))
 119     {
 120       __set_errno (ENOTTY);
 121       return ENOTTY;
 122     }
 123
 124   if (fstat (fd, &st) < 0)
 125     return errno;
 126
 127   /* Prepare the result buffer.  */
 128   memcpy (buf, dev, sizeof (dev) - 1);
 129   buf[sizeof (dev) - 1] = '/';
 130   buflen -= sizeof (dev);
 131
 132 #ifdef _STATBUF_ST_RDEV
 133   ret = getttyname_r (fd, buf, buflen, st.st_rdev, st.st_ino, save,
 134                       &dostat);
 135 #else
 136   ret = getttyname_r (fd, buf, buflen, st.st_dev, st.st_ino, save,
 137                       &dostat);
 138 #endif
 139
 140   if (ret && dostat != -1)
 141     {
 142       dostat = 1;
 143 #ifdef _STATBUF_ST_RDEV
 144       ret = getttyname_r (fd, buf, buflen, st.st_rdev, st.st_ino,
 145                           save, &dostat);
 146 #else
 147       ret = getttyname_r (fd, buf, buflen, st.st_dev, st.st_ino,
 148                           save, &dostat);
 149 #endif
 150     }
 151
 152   return ret;
 153 }
 154
 155 weak_alias (__ttyname_r, ttyname_r)