1/* closexec.c - set or clear the close-on-exec descriptor flag
2
3   Copyright (C) 1991, 2004-2006, 2009-2012 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   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
38int
39set_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
79int
80dup_cloexec (int fd)
81{
82  return fcntl (fd, F_DUPFD_CLOEXEC, 0);
83}
84