grantpt - grant access to the slave pseudoterminal

       For an explanation of the terms used in this section, see attributes(7).
       ┌──────────────────────────────────────────────────────────────────────┬───────────────┬────────────────┐
       │ Interface                                                            │ Attribute     │ Value          │
       ├──────────────────────────────────────────────────────────────────────┼───────────────┼────────────────┤
       │ grantpt()                                                            │ Thread safety │ MT-Safe locale │
       └──────────────────────────────────────────────────────────────────────┴───────────────┴────────────────┘

       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.

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.

       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).

       Standard C library (libc, -lc)

       grantpt - grant access to the slave pseudoterminal

       When successful, grantpt() returns 0.  Otherwise, it returns -1 and sets errno to indicate the error.

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

Linux man-pages 6.9.1                              2024-05-26                                         grantpt(3)

       POSIX.1-2008.

#define_XOPEN_SOURCE#include<stdlib.h>intgrantpt(intfd);

   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