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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
       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 pseu-
              doterminal.
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
       This  page  is  part of release 4.15 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)