1/* Return a safer copy of a file descriptor. 2 3 Copyright (C) 2005 Free Software Foundation, Inc. 4 5 This program is free software; you can redistribute it and/or modify 6 it under the terms of the GNU General Public License as published by 7 the Free Software Foundation; either version 2, or (at your option) 8 any later version. 9 10 This program is distributed in the hope that it will be useful, 11 but WITHOUT ANY WARRANTY; without even the implied warranty of 12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 13 GNU General Public License for more details. 14 15 You should have received a copy of the GNU General Public License 16 along with this program; if not, write to the Free Software Foundation, 17 Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */ 18#include <sys/cdefs.h> 19__RCSID("$NetBSD: fd-safer.c,v 1.2 2016/05/17 14:00:09 christos Exp $"); 20 21 22/* Written by Paul Eggert. */ 23 24#ifdef HAVE_CONFIG_H 25# include <config.h> 26#endif 27 28#include "unistd-safer.h" 29 30#include <errno.h> 31 32#include <unistd.h> 33#ifndef STDIN_FILENO 34# define STDIN_FILENO 0 35#endif 36#ifndef STDERR_FILENO 37# define STDERR_FILENO 2 38#endif 39 40/* Return FD, unless FD would be a copy of standard input, output, or 41 error; in that case, return a duplicate of FD, closing FD. On 42 failure to duplicate, close FD, set errno, and return -1. Preserve 43 errno if FD is negative, so that the caller can always inspect 44 errno when the returned value is negative. 45 46 This function is usefully wrapped around functions that return file 47 descriptors, e.g., fd_safer (open ("file", O_RDONLY)). */ 48 49int 50fd_safer (int fd) 51{ 52 if (STDIN_FILENO <= fd && fd <= STDERR_FILENO) 53 { 54 int f = dup_safer (fd); 55 int e = errno; 56 close (fd); 57 errno = e; 58 fd = f; 59 } 60 61 return fd; 62} 63