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/* Return a safer copy of a file descriptor.
Copyright (C) 2005-2006, 2009-2020 Free Software Foundation, Inc.
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>. */
/* Written by Paul Eggert. */
#include <config.h>
#include "unistd-safer.h"
#include <errno.h>
#include <unistd.h>
/* Return FD, unless FD would be a copy of standard input, output, or
error; in that case, return a duplicate of FD, closing FD. On
failure to duplicate, close FD, set errno, and return -1. Preserve
errno if FD is negative, so that the caller can always inspect
errno when the returned value is negative.
This function is usefully wrapped around functions that return file
descriptors, e.g., fd_safer (open ("file", O_RDONLY)). */
int
fd_safer (int fd)
{
if (STDIN_FILENO <= fd && fd <= STDERR_FILENO)
{
int f = dup_safer (fd);
int e = errno;
close (fd);
errno = e;
fd = f;
}
return fd;
}
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