grantpt(3) — Linux manual page


GRANTPT(3)                Linux Programmer's Manual               GRANTPT(3)

NAME         top

       grantpt - grant access to the slave pseudoterminal

SYNOPSIS         top

       #include <stdlib.h>

       int grantpt(int fd);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

           Since glibc 2.24:
               _XOPEN_SOURCE >= 500 ||
                   (_XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED)
           Glibc 2.23 and earlier:

DESCRIPTION         top

       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         top

       When successful, grantpt() returns 0.  Otherwise, it returns -1 and
       sets errno appropriately.

ERRORS         top

       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

VERSIONS         top

       grantpt() is provided in glibc since version 2.1.

ATTRIBUTES         top

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

       │Interface Attribute     Value          │
       │grantpt() │ Thread safety │ MT-Safe locale │

CONFORMING TO         top

       POSIX.1-2001, POSIX.1-2008.

NOTES         top

       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         top

       open(2), posix_openpt(3), ptsname(3), unlockpt(3), pts(4), pty(7)

COLOPHON         top

       This page is part of release 5.08 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

GNU                              2017-09-15                       GRANTPT(3)

Pages that refer to this page: getpt(3)posix_openpt(3)ptsname(3)ptsname_r(3)unlockpt(3)ptmx(4)pts(4)pty(7)