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 19 /* Written by Paul Eggert. */ 20 21 #ifdef HAVE_CONFIG_H 22 # include <config.h> 23 #endif 24 25 #include "unistd-safer.h" 26 27 #include <errno.h> 28 29 #include <unistd.h> 30 #ifndef STDIN_FILENO 31 # define STDIN_FILENO 0 32 #endif 33 #ifndef STDERR_FILENO 34 # define STDERR_FILENO 2 35 #endif 36 37 /* Return FD, unless FD would be a copy of standard input, output, or 38 error; in that case, return a duplicate of FD, closing FD. On 39 failure to duplicate, close FD, set errno, and return -1. Preserve 40 errno if FD is negative, so that the caller can always inspect 41 errno when the returned value is negative. 42 43 This function is usefully wrapped around functions that return file 44 descriptors, e.g., fd_safer (open ("file", O_RDONLY)). */ 45 46 int 47 fd_safer (int fd) 48 { 49 if (STDIN_FILENO <= fd && fd <= STDERR_FILENO) 50 { 51 int f = dup_safer (fd); 52 int e = errno; 53 close (fd); 54 errno = e; 55 fd = f; 56 } 57 58 return fd; 59 } 60
