sysdeps/posix/ttyname.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 #include <set-freeres.h>
  28
  29 char *__ttyname;
  30
  31 static char *getttyname (int fd, dev_t mydev, ino_t myino,
  32                          int save, int *dostat);
  33
  34
  35 static char *getttyname_name;
  36 weak_alias (getttyname_name, __ttyname_freemem_ptr)
  37
  38 static char *
  39 getttyname (int fd, dev_t mydev, ino_t myino, int save, int *dostat)
  40 {
  41   static const char dev[] = "/dev";
  42   static size_t namelen;
  43   struct stat st;
  44   DIR *dirstream;
  45   struct dirent *d;
  46
  47   dirstream = __opendir (dev);
  48   if (dirstream == NULL)
  49     {
  50       *dostat = -1;
  51       return NULL;
  52     }
  53
  54   while ((d = __readdir (dirstream)) != NULL)
  55     if (((ino_t) d->d_fileno == myino || *dostat)
  56         && strcmp (d->d_name, "stdin")
  57         && strcmp (d->d_name, "stdout")
  58         && strcmp (d->d_name, "stderr"))
  59       {
  60         size_t dlen = _D_ALLOC_NAMLEN (d);
  61         if (sizeof (dev) + dlen > namelen)
  62           {
  63             free (getttyname_name);
  64             namelen = 2 * (sizeof (dev) + dlen); /* Big enough.  */
  65             getttyname_name = malloc (namelen);
  66             if (! getttyname_name)
  67               {
  68                 *dostat = -1;
  69                 /* Perhaps it helps to free the directory stream buffer.  */
  70                 (void) __closedir (dirstream);
  71                 return NULL;
  72               }
  73             *((char *) __mempcpy (getttyname_name, dev, sizeof (dev) - 1))
  74               = '/';
  75           }
  76         (void) __mempcpy (&getttyname_name[sizeof (dev)], d->d_name, dlen);
  77         if (stat (getttyname_name, &st) == 0
  78 #ifdef _STATBUF_ST_RDEV
  79             && S_ISCHR (st.st_mode) && st.st_rdev == mydev
  80 #else
  81             && (ino_t) d->d_fileno == myino && st.st_dev == mydev
  82 #endif
  83            )
  84           {
  85             (void) __closedir (dirstream);
  86             __ttyname = getttyname_name;
  87             __set_errno (save);
  88             return getttyname_name;
  89           }
  90       }
  91
  92   (void) __closedir (dirstream);
  93   __set_errno (save);
  94   return NULL;
  95 }
  96
  97 /* Return the pathname of the terminal FD is open on, or NULL on errors.
  98    The returned storage is good only until the next call to this function.  */
  99 char *
 100 ttyname (int fd)
 101 {
 102   struct stat st;
 103   int dostat = 0;
 104   char *name;
 105   int save = errno;
 106
 107   if (!__isatty (fd))
 108     return NULL;
 109
 110   if (fstat (fd, &st) < 0)
 111     return NULL;
 112
 113 #ifdef _STATBUF_ST_RDEV
 114   name = getttyname (fd, st.st_rdev, st.st_ino, save, &dostat);
 115 #else
 116   name = getttyname (fd, st.st_dev, st.st_ino, save, &dostat);
 117 #endif
 118
 119   if (!name && dostat != -1)
 120     {
 121       dostat = 1;
 122 #ifdef _STATBUF_ST_RDEV
 123       name = getttyname (fd, st.st_rdev, st.st_ino, save, &dostat);
 124 #else
 125       name = getttyname (fd, st.st_dev, st.st_ino, save, &dostat);
 126 #endif
 127     }
 128
 129   return name;
 130 }