GRANTPT
Section: Linux Programmer's Manual (3)
Updated: 2017-09-15
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NAME
grantpt - grant access to the slave pseudoterminal
SYNOPSIS
#include <stdlib.h>
int grantpt(int fd);
Feature Test Macro Requirements for glibc (see
feature_test_macros(7)):
grantpt():
-
Since glibc 2.24:
_XOPEN_SOURCE >= 500 ||
(_XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED)
Glibc 2.23 and earlier:
_XOPEN_SOURCE
DESCRIPTION
The
grantpt()
function changes the mode and owner of the slave pseudoterminal device
corresponding to the master pseudoterminal referred to by
fd.
The user ID of the slave is set to the real UID of the calling process.
The group ID is set to an unspecified value (e.g.,
tty).
The mode of the slave is set to 0620 (crw--w----).
The behavior of
grantpt()
is unspecified if a signal handler is installed to catch
SIGCHLD
signals.
RETURN VALUE
When successful,
grantpt()
returns 0.
Otherwise, it returns -1 and sets
errno
appropriately.
ERRORS
- EACCES
-
The corresponding slave pseudoterminal could not be accessed.
- EBADF
-
The
fd
argument is not a valid open file descriptor.
- EINVAL
-
The
fd
argument is valid but not associated with a master pseudoterminal.
VERSIONS
grantpt()
is provided in glibc since version 2.1.
ATTRIBUTES
For an explanation of the terms used in this section, see
attributes(7).
| Interface | Attribute | Value
|
|
grantpt()
| Thread safety | MT-Safe locale
|
CONFORMING TO
POSIX.1-2001, POSIX.1-2008.
NOTES
This is part of the UNIX 98 pseudoterminal support, see
pts(4).
Many systems implement this function via a set-user-ID helper binary
called "pt_chown".
On Linux systems with a devpts filesystem (present since Linux 2.2),
the kernel normally sets the correct ownership and permissions
for the pseudoterminal slave when the master is opened
(posix_openpt(3)),
so that nothing must be done by
grantpt().
Thus, no such helper binary is required
(and indeed it is configured to be absent during the
glibc build that is typical on many systems).
SEE ALSO
open(2),
posix_openpt(3),
ptsname(3),
unlockpt(3),
pts(4),
pty(7)
COLOPHON
This page is part of release 4.13 of the Linux
man-pages
project.
A description of the project,
information about reporting bugs,
and the latest version of this page,
can be found at
https://www.kernel.org/doc/man-pages/.
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- RETURN VALUE
-
- ERRORS
-
- VERSIONS
-
- ATTRIBUTES
-
- CONFORMING TO
-
- NOTES
-
- SEE ALSO
-
- COLOPHON
-
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