glibc/sysdeps/posix/ttyname_r.c

/* Copyright (C) 1991-2023 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, see
   <https://www.gnu.org/licenses/>.  */

#include <errno.h>
#include <limits.h>
#include <stddef.h>
#include <dirent.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>

#ifndef MIN
# define MIN(a, b) ((a) < (b) ? (a) : (b))
#endif

static const char dev[] = "/dev";

static int getttyname_r (int fd, char *buf, size_t buflen,
			 dev_t mydev, ino_t myino, int save,
			 int *dostat) __THROW;

static int
getttyname_r (int fd, char *buf, size_t buflen, dev_t mydev, ino_t myino,
	      int save, int *dostat)
{
  struct stat st;
  DIR *dirstream;
  struct dirent *d;

  dirstream = __opendir (dev);
  if (dirstream == NULL)
    {
      *dostat = -1;
      return errno;
    }

  while ((d = __readdir (dirstream)) != NULL)
    if (((ino_t) d->d_fileno == myino || *dostat)
	&& strcmp (d->d_name, "stdin")
	&& strcmp (d->d_name, "stdout")
	&& strcmp (d->d_name, "stderr"))
      {
	char *cp;
	size_t needed = _D_EXACT_NAMLEN (d) + 1;

	if (needed > buflen)
	  {
	    *dostat = -1;
	    (void) __closedir (dirstream);
	    __set_errno (ERANGE);
	    return ERANGE;
	  }

	cp = __stpncpy (&buf[sizeof (dev)], d->d_name, needed);
	cp[0] = '\0';

	if (stat (buf, &st) == 0
#ifdef _STATBUF_ST_RDEV
	    && S_ISCHR (st.st_mode) && st.st_rdev == mydev
#else
	    && (ino_t) d->d_fileno == myino && st.st_dev == mydev
#endif
	   )
	  {
	    (void) __closedir (dirstream);
	    __set_errno (save);
	    return 0;
	  }
      }

  (void) __closedir (dirstream);
  __set_errno (save);
  /* It is not clear what to return in this case.  `isatty' says FD
     refers to a TTY but no entry in /dev has this inode.  */
  return ENOTTY;
}

/* Store at most BUFLEN character of the pathname of the terminal FD is
   open on in BUF.  Return 0 on success,  otherwise an error number.  */
int
__ttyname_r (int fd, char *buf, size_t buflen)
{
  struct stat st;
  int dostat = 0;
  int save = errno;
  int ret;

  /* Test for the absolute minimal size.  This makes life easier inside
     the loop.  */
  if (!buf)
    {
      __set_errno (EINVAL);
      return EINVAL;
    }

  if (buflen < (int) (sizeof (dev) + 1))
    {
      __set_errno (ERANGE);
      return ERANGE;
    }

  if (!__isatty (fd))
    {
      __set_errno (ENOTTY);
      return ENOTTY;
    }

  if (fstat (fd, &st) < 0)
    return errno;

  /* Prepare the result buffer.  */
  memcpy (buf, dev, sizeof (dev) - 1);
  buf[sizeof (dev) - 1] = '/';
  buflen -= sizeof (dev);

#ifdef _STATBUF_ST_RDEV
  ret = getttyname_r (fd, buf, buflen, st.st_rdev, st.st_ino, save,
		      &dostat);
#else
  ret = getttyname_r (fd, buf, buflen, st.st_dev, st.st_ino, save,
		      &dostat);
#endif

  if (ret && dostat != -1)
    {
      dostat = 1;
#ifdef _STATBUF_ST_RDEV
      ret = getttyname_r (fd, buf, buflen, st.st_rdev, st.st_ino,
			  save, &dostat);
#else
      ret = getttyname_r (fd, buf, buflen, st.st_dev, st.st_ino,
			  save, &dostat);
#endif
    }

  return ret;
}

weak_alias (__ttyname_r, ttyname_r)