grantpt(3)                 Library Functions Manual                 grantpt(3)

NAME
       grantpt - grant access to the slave pseudoterminal

LIBRARY
       Standard C library (libc, -lc)

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
           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)

Linux man-pages 6.7               2023-10-31                        grantpt(3)