GRANTPT(3) Library Functions Manual GRANTPT(3)

grantpt, posix_openpt, ptsname, ptsname_r, unlockpt — pseudo-terminal access functions

#include <stdlib.h>

int
grantpt(int fildes);

char *
ptsname(int fildes);

int
ptsname_r(int fildes, char *buffer, size_t buflen);

int
unlockpt(int fildes);

#include <stdlib.h>
#include <fcntl.h>

int
posix_openpt(int oflag);

The (), ptsname(), (), unlockpt(), and posix_openpt() functions allow access to pseudo-terminal devices. The first four functions accept a file descriptor that references the primary half of a pseudo-terminal pair. This file descriptor is created with posix_openpt().

The () function is used to establish ownership and permissions of the replica device counterpart to the primary device specified with fildes. The replica device's ownership is set to the real user ID of the calling process; its permissions are set to user readable-writable and group writable. The group owner of the replica device is also set to the group “tty” if it exists on the system; otherwise, it is left untouched.

The () function returns a pointer to the full pathname of the replica device counterpart to the primary device specified with fildes. This value can be used to subsequently open the appropriate replica after posix_openpt() and grantpt() have been called. The ptsname() function is not guaranteed to be reentrant or thread safe. The ptsname_r() function stores the full pathname of the replica device in the buffer pointed to by its buffer argument, up to a maximum length of buflen including the terminating NUL.

The () function unlocks the replica pseudo-terminal device associated with the primary device to which fildes refers.

The () function opens the first available primary pseudo-terminal device and returns a descriptor to it. The oflag argument specifies the flags used for opening the device:

Open for reading and writing.
If set, do not allow the terminal to become the controlling terminal for the calling process.

The grantpt() and unlockpt() functions return the value 0 if successful; otherwise the value -1 is returned and the global variable errno is set to indicate the error.

The ptsname() function returns a pointer to the name of the replica device on success; otherwise a NULL pointer is returned and the global variable errno is set to indicate the error.

The ptsname_r() function returns 0 if successful. On failure, it returns -1 and the global variable errno is set to indicate the error.

The posix_openpt() function returns a file descriptor to the first available primary pseudo-terminal device on success; otherwise -1 is returned and the global variable errno is set to indicate the error.

The grantpt(), ptsname(), ptsname_r(), and unlockpt() functions may fail and set errno to:

[]
fildes is not a primary pseudo-terminal device.

In addition, the ptsname_r() function may set errno to:

[]
The buffer argument is NULL.
[]
The buflen argument is smaller than the length of the string to be returned, including the terminating NUL.

In addition, the grantpt() function may set errno to:

[]
The replica pseudo-terminal device could not be accessed.

The posix_openpt() function may fail and set errno to:

[]
oflag consists of an invalid mode bit.
[]
The system has no available pseudo-terminal devices.
[]
The sysctl(3) limit “kern.tty.ptmx_max” number of pseudo-terminal devices was reached.

The grantpt(), ptsname(), ptsname_r(), and unlockpt() functions may also fail and set errno for any of the errors specified for the fstat(2) system call.

The posix_openpt() function may also fail and set errno for any of the errors specified for the open(2) system call.

#include <stdlib.h> #include <fcntl.h>

int
(int fildes);;

char *
(int fildes);;

int
(int fildes);;

#include <fcntl.h>

int
(int oflag);;

open(2), sysctl(3), pty(4), tty(4), compat(5)

The grantpt(), ptsname(), unlockpt(), and posix_openpt() functions conform to IEEE Std 1003.1-2001 (“POSIX.1”).

February 2, 2005 Mac OS X 12