GRANTPT(3) Linux Programmer's Manual GRANTPT(3)
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 pseu-
doterminal device corresponding to the master pseudoterminal referred
to by fd. The user ID of the slave is set to the real UID of the call-
ing 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 in-
stalled 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 pseu-
doterminal.
VERSIONS
grantpt() is provided in glibc since version 2.1.
ATTRIBUTES
For an explanation of the terms used in this section, see at-
tributes(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 ab-
sent 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 5.07 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/.
GNU 2017-09-15 GRANTPT(3)