grantpt - grant access to the slave pseudoterminal
#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
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.
When successful,
grantpt() returns 0. Otherwise, it returns -1 and sets
errno appropriately.
- 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.
grantpt() is provided in glibc since version 2.1.
For an explanation of the terms used in this section, see
attributes(7).
| Interface |
Attribute |
Value |
| grantpt () |
Thread safety |
MT-Safe locale |
POSIX.1-2001, POSIX.1-2008.
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).
open(2),
posix_openpt(3),
ptsname(3),
unlockpt(3),
pts(4),
pty(7)