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6ec2e0f5 SDJ |
1 | /* Return a safer copy of a file descriptor. |
2 | ||
3 | Copyright (C) 2005-2006, 2009-2016 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 <http://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 | } |