| 1 | /* Return a safer copy of a file descriptor. |
| 2 | |
| 3 | Copyright (C) 2005-2006, 2009-2020 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 3 of the License, or |
| 8 | (at your option) 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, see <https://www.gnu.org/licenses/>. */ |
| 17 | |
| 18 | /* Written by Paul Eggert. */ |
| 19 | |
| 20 | #include <config.h> |
| 21 | |
| 22 | #include "unistd-safer.h" |
| 23 | |
| 24 | #include <errno.h> |
| 25 | #include <unistd.h> |
| 26 | |
| 27 | /* Return FD, unless FD would be a copy of standard input, output, or |
| 28 | error; in that case, return a duplicate of FD, closing FD. On |
| 29 | failure to duplicate, close FD, set errno, and return -1. Preserve |
| 30 | errno if FD is negative, so that the caller can always inspect |
| 31 | errno when the returned value is negative. |
| 32 | |
| 33 | This function is usefully wrapped around functions that return file |
| 34 | descriptors, e.g., fd_safer (open ("file", O_RDONLY)). */ |
| 35 | |
| 36 | int |
| 37 | fd_safer (int fd) |
| 38 | { |
| 39 | if (STDIN_FILENO <= fd && fd <= STDERR_FILENO) |
| 40 | { |
| 41 | int f = dup_safer (fd); |
| 42 | int e = errno; |
| 43 | close (fd); |
| 44 | errno = e; |
| 45 | fd = f; |
| 46 | } |
| 47 | |
| 48 | return fd; |
| 49 | } |