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PTSNAME(3)            DragonFly Library Functions Manual            PTSNAME(3)


NAME

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


LIBRARY

     Standard C Library (libc, -lc)


SYNOPSIS

     #include <stdlib.h>

     int
     grantpt(int fildes);

     char *
     ptsname(int fildes);

     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
     descriptor is created with posix_openpt(3) or by calling open(2) on
     /dev/ptmx.

     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(3)
     and grantpt() have been called.

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


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.


ERRORS

     The grantpt() 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 grantpt() function may set errno to:

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


SEE ALSO

     posix_openpt(3), 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(3) 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
     DragonFly 2.3.

DragonFly 3.5                 September 10, 2009                 DragonFly 3.5

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