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 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.

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 pseudoterminal.

VERSIONS

       grantpt() is provided in glibc since version 2.1.

ATTRIBUTES

       For an explanation of the terms used in this section, see attributes(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
       absent 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

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