lib/isatty.c

   1 /* isatty() replacement.
   2    Copyright (C) 2012-2019 Free Software Foundation, Inc.
   3
   4    This program is free software: you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation; either version 3 of the License, or
   7    (at your option) any later version.
   8
   9    This program 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
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License
  15    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  16
  17 #include <config.h>
  18
  19 /* Specification.  */
  20 #include <unistd.h>
  21
  22 /* This replacement is enabled on native Windows.  */
  23
  24 #include <errno.h>
  25
  26 /* Get declarations of the Win32 API functions.  */
  27 #define WIN32_LEAN_AND_MEAN
  28 #include <windows.h>
  29
  30 #if HAVE_MSVC_INVALID_PARAMETER_HANDLER
  31 # include "msvc-inval.h"
  32 #endif
  33
  34 /* Get _get_osfhandle().  */
  35 #if GNULIB_MSVC_NOTHROW
  36 # include "msvc-nothrow.h"
  37 #else
  38 # include <io.h>
  39 #endif
  40
  41 static BOOL IsConsoleHandle (HANDLE h)
  42 {
  43   DWORD mode;
  44   return GetConsoleMode (h, &mode) != 0;
  45 }
  46
  47 #if HAVE_MSVC_INVALID_PARAMETER_HANDLER
  48 static int
  49 _isatty_nothrow (int fd)
  50 {
  51   int result;
  52
  53   TRY_MSVC_INVAL
  54     {
  55       result = _isatty (fd);
  56     }
  57   CATCH_MSVC_INVAL
  58     {
  59       result = 0;
  60     }
  61   DONE_MSVC_INVAL;
  62
  63   return result;
  64 }
  65 #else
  66 # define _isatty_nothrow _isatty
  67 #endif
  68
  69 /* Determine whether FD refers to a console device.  Return 1 if yes.
  70    Return 0 and set errno if no. (ptsname_r relies on the errno value.)  */
  71 int
  72 isatty (int fd)
  73 {
  74   HANDLE h = (HANDLE) _get_osfhandle (fd);
  75   if (h == INVALID_HANDLE_VALUE)
  76     {
  77       errno = EBADF;
  78       return 0;
  79     }
  80   /* _isatty (fd) tests whether GetFileType of the handle is FILE_TYPE_CHAR.
  81      But it does not set errno when it returns 0.  */
  82   if (_isatty_nothrow (fd))
  83     {
  84       if (IsConsoleHandle (h))
  85         return 1;
  86     }
  87   errno = ENOTTY;
  88   return 0;
  89 }