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
23 extern void
tuklib_open_stdxxx(int err_status)24 tuklib_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