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

       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/.