1///////////////////////////////////////////////////////////////////////////////
2//
3/// \file       tuklib_open_stdxxx.c
4/// \brief      Make sure that file descriptors 0, 1, and 2 are open
5//
6//  Author:     Lasse Collin
7//
8//  This file has been put into the public domain.
9//  You can do whatever you want with this file.
10//
11///////////////////////////////////////////////////////////////////////////////
12
13#include "tuklib_open_stdxxx.h"
14
15#ifndef TUKLIB_DOSLIKE
16#	include <stdlib.h>
17#	include <errno.h>
18#	include <fcntl.h>
19#	include <unistd.h>
20#endif
21
22
23extern void
24tuklib_open_stdxxx(int err_status)
25{
26#ifdef TUKLIB_DOSLIKE
27	// Do nothing, just silence warnings.
28	(void)err_status;
29
30#else
31	for (int i = 0; i <= 2; ++i) {
32		// We use fcntl() to check if the file descriptor is open.
33		if (fcntl(i, F_GETFD) == -1 && errno == EBADF) {
34			// With stdin, we could use /dev/full so that
35			// writing to stdin would fail. However, /dev/full
36			// is Linux specific, and if the program tries to
37			// write to stdin, there's already a problem anyway.
38			const int fd = open("/dev/null", O_NOCTTY
39					| (i == 0 ? O_WRONLY : O_RDONLY));
40
41			if (fd != i) {
42				if (fd != -1)
43					(void)close(fd);
44
45				// Something went wrong. Exit with the
46				// exit status we were given. Don't try
47				// to print an error message, since stderr
48				// may very well be non-existent. This
49				// error should be extremely rare.
50				exit(err_status);
51			}
52		}
53	}
54#endif
55
56	return;
57}
58