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+/* Return a safer copy of a file descriptor.
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+
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+ Copyright (C) 2005 Free Software Foundation, Inc.
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+
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+ This program is free software; you can redistribute it and/or modify
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+ it under the terms of the GNU General Public License as published by
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+ the Free Software Foundation; either version 2, or (at your option)
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+ any later version.
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+
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+ This program is distributed in the hope that it will be useful,
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+ but WITHOUT ANY WARRANTY; without even the implied warranty of
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+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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+ GNU General Public License for more details.
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+
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+ You should have received a copy of the GNU General Public License
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+ along with this program; if not, write to the Free Software Foundation,
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+ Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
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+
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+/* Written by Paul Eggert. */
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+
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+#ifdef HAVE_CONFIG_H
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+# include <config.h>
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+#endif
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+
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+#include "unistd-safer.h"
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+
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+#include <errno.h>
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+
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+#include <unistd.h>
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+#ifndef STDIN_FILENO
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+# define STDIN_FILENO 0
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+#endif
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+#ifndef STDERR_FILENO
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+# define STDERR_FILENO 2
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+#endif
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+
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+/* Return FD, unless FD would be a copy of standard input, output, or
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+ error; in that case, return a duplicate of FD, closing FD. On
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+ failure to duplicate, close FD, set errno, and return -1. Preserve
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+ errno if FD is negative, so that the caller can always inspect
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+ errno when the returned value is negative.
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+
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+ This function is usefully wrapped around functions that return file
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+ descriptors, e.g., fd_safer (open ("file", O_RDONLY)). */
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+
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+int
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+fd_safer (int fd)
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+{
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+ if (STDIN_FILENO <= fd && fd <= STDERR_FILENO)
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+ {
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+ int f = dup_safer (fd);
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+ int e = errno;
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+ close (fd);
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+ errno = e;
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+ fd = f;
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+ }
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+
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+ return fd;
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+}
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