root/src/common/tuklib_open_stdxxx.c

DEFINITIONS

1. tuklib_open_stdxxx

///////////////////////////////////////////////////////////////////////////////
//
/// \file       tuklib_open_stdxxx.c
/// \brief      Make sure that file descriptors 0, 1, and 2 are open
//
//  Author:     Lasse Collin
//
//  This file has been put into the public domain.
//  You can do whatever you want with this file.
//
///////////////////////////////////////////////////////////////////////////////

#include "tuklib_open_stdxxx.h"

#ifndef TUKLIB_DOSLIKE
#       include <stdlib.h>
#       include <errno.h>
#       include <fcntl.h>
#       include <unistd.h>
#endif


extern void
tuklib_open_stdxxx(int err_status)
{
#ifdef TUKLIB_DOSLIKE
        // Do nothing, just silence warnings.
        (void)err_status;

#else
        for (int i = 0; i <= 2; ++i) {
                // We use fcntl() to check if the file descriptor is open.
                if (fcntl(i, F_GETFD) == -1 && errno == EBADF) {
                        // With stdin, we could use /dev/full so that
                        // writing to stdin would fail. However, /dev/full
                        // is Linux specific, and if the program tries to
                        // write to stdin, there's already a problem anyway.
                        const int fd = open("/dev/null", O_NOCTTY
                                        | (i == 0 ? O_WRONLY : O_RDONLY));

                        if (fd != i) {
                                if (fd != -1)
                                        (void)close(fd);

                                // Something went wrong. Exit with the
                                // exit status we were given. Don't try
                                // to print an error message, since stderr
                                // may very well be non-existent. This
                                // error should be extremely rare.
                                exit(err_status);
                        }
                }
        }
#endif

        return;
}