grantpt(3) BSD Library Functions Manual grantpt(3)
NAME
grantpt, posix_openpt, ptsname, unlockpt -- pseudo-terminal access func-
tions
SYNOPSIS
#include <stdlib.h>
int
grantpt(int fildes);
char *
ptsname(int fildes);
int
unlockpt(int fildes);
#include <stdlib.h>
#include <fcntl.h>
int
posix_openpt(int oflag);
DESCRIPTION
The grantpt(), ptsname(), unlockpt(), and posix_openpt() functions allow
access to pseudo-terminal devices. The first three functions accept a
file descriptor that references the master half of a pseudo-terminal
pair. This file descriptor is created with posix_openpt().
The grantpt() function is used to establish ownership and permissions of
the slave device counterpart to the master device specified with fildes.
The slave 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 slave device is also set to the group
``tty'' if it exists on the system; otherwise, it is left untouched.
The ptsname() function returns the full pathname of the slave device
counterpart to the master device specified with fildes. This value can
be used to subsequently open the appropriate slave after posix_openpt()
and grantpt() have been called.
The unlockpt() function unlocks the slave pseudo-terminal device associ-
ated with the master device to which fildes refers.
The posix_openpt() function opens the first available master pseudo-ter-
minal device and returns a descriptor to it. The oflag argument speci-
fies the flags used for opening the device:
O_RDWR Open for reading and writing.
O_NOCTTY If set, do not allow the terminal to become the controlling
terminal for the calling process.
RETURN VALUES
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 slave device
on success; otherwise a NULL pointer is returned and the global variable
errno is set to indicate the error.
The posix_openpt() function returns a file descriptor to the first avail-
able master pseudo-terminal device on success; otherwise -1 is returned
and the global variable errno is set to indicate the error.
ERRORS
The grantpt(), ptsname(), and unlockpt() functions may fail and set errno
to:
[EINVAL] fildes is not a master pseudo-terminal device.
In addition, the grantpt() function may set errno to:
[EACCES] The slave pseudo-terminal device could not be
accessed.
The posix_openpt() function may fail and set errno to:
[EINVAL] oflag consists of an invalid mode bit.
[EAGAIN] The system has no available pseudo-terminal devices.
The grantpt(), ptsname(), 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.
LEGACY SYNOPSIS
#include <stdlib.h>
#include <fcntl.h>
int
grantpt(int fildes);
char *
ptsname(int fildes);
int
unlockpt(int fildes);
#include <fcntl.h>
int
posix_openpt(int oflag);
SEE ALSO
open(2), pty(4), tty(4), compat(5)
STANDARDS
The grantpt(), ptsname(), unlockpt(), and posix_openpt() functions con-
form to IEEE Std 1003.1-2001 (``POSIX.1'').
BSD February 2, 2005 BSD
Mac OS X 10.8 - Generated Tue Aug 28 05:46:39 CDT 2012