1 | /* Adjust a file descriptor result so that it avoids clobbering |
2 | STD{IN,OUT,ERR}_FILENO, with specific flags. |
3 | |
4 | Copyright (C) 2005-2006, 2009-2019 Free Software Foundation, Inc. |
5 | |
6 | This program is free software: you can redistribute it and/or modify |
7 | it under the terms of the GNU General Public License as published by |
8 | the Free Software Foundation; either version 3 of the License, or |
9 | (at your option) any later version. |
10 | |
11 | This program is distributed in the hope that it will be useful, |
12 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
13 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
14 | GNU General Public License for more details. |
15 | |
16 | You should have received a copy of the GNU General Public License |
17 | along with this program. If not, see <https://www.gnu.org/licenses/>. */ |
18 | |
19 | /* Written by Paul Eggert and Eric Blake. */ |
20 | |
21 | #include <config.h> |
22 | |
23 | /* Specification. */ |
24 | #include "unistd-safer.h" |
25 | |
26 | #include <errno.h> |
27 | #include <unistd.h> |
28 | |
29 | /* Return FD, unless FD would be a copy of standard input, output, or |
30 | error; in that case, return a duplicate of FD, closing FD. If FLAG |
31 | contains O_CLOEXEC, the returned FD will have close-on-exec |
32 | semantics. On failure to duplicate, close FD, set errno, and |
33 | return -1. Preserve errno if FD is negative, so that the caller |
34 | can always inspect errno when the returned value is negative. |
35 | |
36 | This function is usefully wrapped around functions that return file |
37 | descriptors, e.g., fd_safer_flag (open ("file", O_RDONLY | flag), flag). */ |
38 | |
39 | int |
40 | fd_safer_flag (int fd, int flag) |
41 | { |
42 | if (STDIN_FILENO <= fd && fd <= STDERR_FILENO) |
43 | { |
44 | int f = dup_safer_flag (fd, flag); |
45 | int e = errno; |
46 | close (fd); |
47 | errno = e; |
48 | fd = f; |
49 | } |
50 | |
51 | return fd; |
52 | } |
53 | |