tuklib_open_stdxxx.c

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//
//
//  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;
}