1 /* cloexec.c - set or clear the close-on-exec descriptor flag
2
3 Copyright (C) 1991, 2004-2006, 2009-2023 Free Software Foundation,
4 Inc.
5
6 This file is free software: you can redistribute it and/or modify
7 it under the terms of the GNU Lesser General Public License as
8 published by the Free Software Foundation; either version 2.1 of the
9 License, or (at your option) any later version.
10
11 This file 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 Lesser General Public License for more details.
15
16 You should have received a copy of the GNU Lesser General Public License
17 along with this program. If not, see <https://www.gnu.org/licenses/>. */
18
19 /* The code is taken from glibc/manual/llio.texi */
20
21 #include <config.h>
22
23 #include "cloexec.h"
24
25 #include <errno.h>
26 #include <fcntl.h>
27 #include <unistd.h>
28
29 /* Set the 'FD_CLOEXEC' flag of DESC if VALUE is true,
30 or clear the flag if VALUE is false.
31 Return 0 on success, or -1 on error with 'errno' set.
32
33 Note that on MingW, this function does NOT protect DESC from being
34 inherited into spawned children. Instead, either use dup_cloexec
35 followed by closing the original DESC, or use interfaces such as
36 open or pipe2 that accept flags like O_CLOEXEC to create DESC
37 non-inheritable in the first place. */
38
39 int
40 set_cloexec_flag (int desc, bool value)
41 {
42 #ifdef F_SETFD
43
44 int flags = fcntl (desc, F_GETFD, 0);
45
46 if (0 <= flags)
47 {
48 int newflags = (value ? flags | FD_CLOEXEC : flags & ~FD_CLOEXEC);
49
50 if (flags == newflags
51 || fcntl (desc, F_SETFD, newflags) != -1)
52 return 0;
53 }
54
55 return -1;
56
57 #else /* !F_SETFD */
58
59 /* Use dup2 to reject invalid file descriptors; the cloexec flag
60 will be unaffected. */
61 if (desc < 0)
62 {
63 errno = EBADF;
64 return -1;
65 }
66 if (dup2 (desc, desc) < 0)
67 /* errno is EBADF here. */
68 return -1;
69
70 /* There is nothing we can do on this kind of platform. Punt. */
71 return 0;
72 #endif /* !F_SETFD */
73 }
74
75
76 /* Duplicates a file handle FD, while marking the copy to be closed
77 prior to exec or spawn. Returns -1 and sets errno if FD could not
78 be duplicated. */
79
80 int
81 dup_cloexec (int fd)
82 {
83 return fcntl (fd, F_DUPFD_CLOEXEC, 0);
84 }