rm_/lib/freopen.c

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/* Open a stream to a file.
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Copyright (C) 2007-2022 Free Software Foundation, Inc.
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This file is free software: you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as
published by the Free Software Foundation, either version 3 of the
License, or (at your option) any later version.
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This file is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with this program. If not, see <https://www.gnu.org/licenses/>. */
/* Written by Bruno Haible <bruno@clisp.org>, 2007. */
/* If the user's config.h happens to include <stdio.h>, let it include only
the system's <stdio.h> here, so that orig_freopen doesn't recurse to
rpl_freopen. */
#define _GL_ALREADY_INCLUDING_STDIO_H
#include <config.h>
/* Get the original definition of freopen. It might be defined as a macro. */
#include <stdio.h>
#undef _GL_ALREADY_INCLUDING_STDIO_H
#include <errno.h>
static FILE *
orig_freopen (const char *filename, const char *mode, FILE *stream)
{
return freopen (filename, mode, stream);
}
/* Specification. */
/* Write "stdio.h" here, not <stdio.h>, otherwise OSF/1 5.1 DTK cc eliminates
this include because of the preliminary #include <stdio.h> above. */
#include "stdio.h"
#include <fcntl.h>
#include <string.h>
#include <unistd.h>
FILE *
rpl_freopen (const char *filename, const char *mode, FILE *stream)
{
FILE *result;
#if defined _WIN32 && ! defined __CYGWIN__
char const *null_device = "NUL";
if (filename && strcmp (filename, "/dev/null") == 0)
filename = null_device;
#else
char const *null_device = "/dev/null";
#endif
#ifdef __KLIBC__
errno = 0;
#endif
result = orig_freopen (filename, mode, stream);
if (!result)
{
#ifdef __KLIBC__
/* On OS/2 kLIBC, freopen returns NULL even if it is successful
if filename is NULL. */
if (!filename && !errno)
result = stream;
#endif
}
else if (filename)
{
int fd = fileno (result);
if (dup2 (fd, fd) < 0 && errno == EBADF)
{
int nullfd = open (null_device, O_RDONLY | O_CLOEXEC);
int err = 0;
if (nullfd != fd)
{
if (dup2 (nullfd, fd) < 0)
err = 1;
close (nullfd);
}
if (!err)
result = orig_freopen (filename, mode, result);
}
}
return result;
}