1 /* cloexec.c - set or clear the close-on-exec descriptor flag
2
3 Copyright (C) 1991, 2004-2006, 2009-2023 Free Software Foundation, Inc.
4
5 This file is free software: you can redistribute it and/or modify
6 it under the terms of the GNU Lesser General Public License as
7 published by the Free Software Foundation; either version 2.1 of the
8 License, or (at your option) any later version.
9
10 This file 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 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public License
16 along with this program. If not, see <https://www.gnu.org/licenses/>. */
17
18 /* The code is taken from glibc/manual/llio.texi */
19
20 #include <config.h>
21
22 #include "cloexec.h"
23
24 #include <errno.h>
25 #include <fcntl.h>
26 #include <unistd.h>
27
28 /* Set the 'FD_CLOEXEC' flag of DESC if VALUE is true,
29 or clear the flag if VALUE is false.
30 Return 0 on success, or -1 on error with 'errno' set.
31
32 Note that on MingW, this function does NOT protect DESC from being
33 inherited into spawned children. Instead, either use dup_cloexec
34 followed by closing the original DESC, or use interfaces such as
35 open or pipe2 that accept flags like O_CLOEXEC to create DESC
36 non-inheritable in the first place. */
37
38 int
39 set_cloexec_flag (int desc, bool value)
40 {
41 #ifdef F_SETFD
42
43 int flags = fcntl (desc, F_GETFD, 0);
44
45 if (0 <= flags)
46 {
47 int newflags = (value ? flags | FD_CLOEXEC : flags & ~FD_CLOEXEC);
48
49 if (flags == newflags
50 || fcntl (desc, F_SETFD, newflags) != -1)
51 return 0;
52 }
53
54 return -1;
55
56 #else /* !F_SETFD */
57
58 /* Use dup2 to reject invalid file descriptors; the cloexec flag
59 will be unaffected. */
60 if (desc < 0)
61 {
62 errno = EBADF;
63 return -1;
64 }
65 if (dup2 (desc, desc) < 0)
66 /* errno is EBADF here. */
67 return -1;
68
69 /* There is nothing we can do on this kind of platform. Punt. */
70 return 0;
71 #endif /* !F_SETFD */
72 }
73
74
75 /* Duplicates a file handle FD, while marking the copy to be closed
76 prior to exec or spawn. Returns -1 and sets errno if FD could not
77 be duplicated. */
78
79 int
80 dup_cloexec (int fd)
81 {
82 return fcntl (fd, F_DUPFD_CLOEXEC, 0);
83 }