NAME    [Toc]    [Back]

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

LIBRARY    [Toc]    [Back]

     Standard C Library (libc, -lc)

SYNOPSIS    [Toc]    [Back]

     #include <stdlib.h>

     int
     grantpt(int fildes);

     char *
     ptsname(int fildes);

     int
     unlockpt(int fildes);

     #include <fcntl.h>

     int
     posix_openpt(int mode);

DESCRIPTION    [Toc]    [Back]

     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, 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 posix_openpt()
     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 posix_openpt() function opens the first available master pseudo-terminal
 device and returns a descriptor to it.  The mode argument specifies
     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    [Toc]    [Back]

     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 available
 master pseudo-terminal device on success; otherwise -1 is returned
     and the global variable errno is set to indicate the error.

ERRORS    [Toc]    [Back]

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

SEE ALSO    [Toc]    [Back]

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

STANDARDS    [Toc]    [Back]

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

HISTORY    [Toc]    [Back]

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

NOTES    [Toc]    [Back]

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

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


FreeBSD 5.2.1		       December 23, 2002		 FreeBSD 5.2.1