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

NAME
     grantpt, ptsname, unlockpt, posixopenpt -- pseudo-terminal access func-
     tions

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     ##include <>
     ##include <>

     int
     grantpt(int fildes);

     char *
     ptsname(int fildes);

     int
     unlockpt(int fildes);

     ##include <>

     int
     posixopenpt(int mode);

DESCRIPTION
     The grantpt(), ptsname(), unlockpt(), and posixopenpt() 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 posixopenpt().

     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, and the 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 posixopenpt()
     and grantpt() have been called.

     The unlockpt() function clears the lock held on the pseudo-terminal pair
     for the master device specified with fildes.

     The posixopenpt() function opens the first available master pseudo-ter-
     minal device and returns a descriptor to it.  The mode argument specifies
     the flags used for opening the device:

     ORDWR    Open for reading and writing.

     ONOCTY  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 NUL pointer is returned and the global variable
     errno is set to indicate the error.

     The posixopenpt() 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.

ERORS
     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:

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

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

     [EINVAL]           mode 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 posixopenpt() function may also fail and set errno for any of the
     errors specified for the open(2) system call.

SEE ALSO
     open(2), pty(4), tty(4)

STANDARDS
     The grantpt(), ptsname(), unlockpt(), and posixopenpt() functions con-
     form to IE Std 1003.1-2001 (``POSIX.1'').

HISTORY
     The grantpt(), ptsname(), unlockpt(), and posixopenpt() functions
     appeared in FreeBSD 5.0.

NOTES
     The purpose of the unlockpt() function has no meaning in FreeBSD.

     The flag ONOCTY is included for compatibility; in FreeBSD, opening a
     terminal does not cause it to become a process's controlling terminal.

BSD                            December 23, 2002                           BSD