1 | /* Return a safer copy of a file descriptor. |
2 | |
3 | Copyright (C) 2005-2006, 2009-2019 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 | } |
50 | |