grantpt(3) — Linux manual page
grantpt(3) Library Functions Manual grantpt(3)
NAME
grantpt - grant access to the slave pseudoterminal
LIBRARY
Standard C library (libc, -lc)
SYNOPSIS
#define _XOPEN_SOURCE
#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
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 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.
RETURN VALUE
When successful, grantpt() returns 0. Otherwise, it returns -1
and sets errno to indicate the error.
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.
ATTRIBUTES
For an explanation of the terms used in this section, see
attributes(7).
┌──────────────────────────────┬───────────────┬────────────────┐
│ Interface │ Attribute │ Value │
├──────────────────────────────┼───────────────┼────────────────┤
│ grantpt() │ Thread safety │ MT-Safe locale │
└──────────────────────────────┴───────────────┴────────────────┘
STANDARDS
POSIX.1-2008.
HISTORY
glibc 2.1. POSIX.1-2001.
This is part of the UNIX 98 pseudoterminal support, see pts(4).
Historical systems implemented this function via a set-user-ID
helper binary called "pt_chown". glibc on Linux before glibc
2.33 could do so as well, in order to support configurations with
only BSD pseudoterminals; this support has been removed. On
modern systems this is either a no-op —with permissions
configured on pty allocation, as is the case on Linux— or an
ioctl(2).
SEE ALSO
open(2), posix_openpt(3), ptsname(3), unlockpt(3), pts(4), pty(7)
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Linux man-pages 6.9.1 2024-05-26 grantpt(3)
Pages that refer to this page: getpt(3), posix_openpt(3), ptsname(3), unlockpt(3), pts(4), pty(7)