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PTSNAME(3)	       FreeBSD Library Functions Manual		    PTSNAME(3)

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

LIBRARY
     Standard C	Library	(libc, -lc)

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);

DESCRIPTION
     The grantpt(), ptsname(), and unlockpt() functions	allow access to
     pseudo-terminal devices.  These three functions accept a file descriptor
     that references the master	half of	a pseudo-terminal pair.	 This file de-
     scriptor is created with posix_openpt(2).

     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".

     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(2)
     and grantpt() have	been called.

     The ptsname_r() function is the thread-safe version of ptsname().	The
     caller must provide storage for the results of the	full pathname of the
     slave device in the buffer	and bufsize arguments.

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

RETURN VALUES
     The grantpt(), ptsname_r(), 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.

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

     [EBADF]		fildes is not a	valid open file	descriptor.

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

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

     [ERANGE]		The buffer was too small.

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

     [EACCES]		The slave pseudo-terminal device could not be ac-
			cessed.

SEE ALSO
     posix_openpt(2), pts(4), tty(4)

STANDARDS
     The ptsname() function conforms to	IEEE Std 1003.1-2008 ("POSIX.1").

     This implementation of grantpt() and unlockpt() does not conform to IEEE
     Std 1003.1-2008 ("POSIX.1"), because it depends on	posix_openpt(2)	to
     create the	pseudo-terminal	device with proper permissions in place.  It
     only validates whether fildes is a	valid pseudo-terminal master device.
     Future revisions of the specification will	likely allow this behaviour,
     as	stated by the Austin Group.

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

FreeBSD	13.0		       October 17, 2020			  FreeBSD 13.0
NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUES | ERRORS | SEE ALSO | STANDARDS | HISTORY

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