GRANTPT(3)               BSD Library Functions Manual               GRANTPT(3)

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

SYNOPSIS
     #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);

DESCRIPTION
     The grantpt(), ptsname(), ptsname_r(), unlockpt(), and posix_openpt()
     functions allow access to pseudo-terminal devices.  The first four func-
     tions 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() and ptsname_r() functions return 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 ptsname() function is
     not guaranteed to be reentrant or thread safe. The ptsname_r() function
     takes a buffer and length as arguments to avoid this problem.

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

     [EINVAL]           fildes is not a master pseudo-terminal device.

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

     [EINVAL]           The buffer argument is NULL.

     [ERANGE]           The bufsize argument is smaller than the length of the
                        string to be returned.

     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(), ptsname_r(), and unlockpt() functions may also
     fail and set errno for any of the errors specified for the fstat(2) sys-
     tem 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