grantpt - grant access to the slave pseudoterminal
Standard C library (
libc,
-lc)
#include <stdlib.h>
int grantpt(int fd);
grantpt():
Since glibc 2.24:
_XOPEN_SOURCE >= 500
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 the file descriptor
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 to indicate the error.
- 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 since glibc 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)