NAME    [Toc]    [Back]

     openpty, forkpty -- auxiliary functions to obtain a pseudo-terminal

LIBRARY    [Toc]    [Back]

     System Utilities Library (libutil, -lutil)

SYNOPSIS    [Toc]    [Back]

     #include <sys/types.h>
     #include <sys/ioctl.h>
     #include <termios.h>
     #include <libutil.h>

     int
     openpty(int *amaster, int *aslave, char *name, struct termios *termp,
	 struct winsize *winp);

     int
     forkpty(int *amaster, char *name, struct termios *termp,
	 struct winsize *winp);

DESCRIPTION    [Toc]    [Back]

     The function openpty() attempts to obtain the next available pseudo-terminal
 from the system (see pty(4)).  If it successfully finds one, it
     subsequently tries to change the ownership of the slave device to the
     real UID of the current process, the group membership to the group
     ``tty'' (if such a group exists in the system), the access permissions
     for reading and writing by the owner, and for writing by the group, and
     to invalidate any current use of the line by calling revoke(2).

     If the argument name is not NULL, openpty() copies the pathname of the
     slave pty to this area.  The caller is responsible for allocating the
     required space in this array.

     If the arguments termp or winp are not NULL, openpty() initializes the
     termios and window size settings from the structures these arguments
     point to, respectively.

     Upon return, the open file descriptors for the master and slave side of
     the pty are returned in the locations pointed to by amaster and aslave,
     respectively.

     The forkpty() function first calls openpty() to obtain the next available
     pseudo-terminal from the system.  Upon success, it forks off a new
     process.  In the child process, it closes the descriptor for the master
     side of the pty, and calls login_tty(3) for the slave pty.  In the parent
     process, it closes the descriptor for the slave side of the pty.  The
     arguments amaster, name, termp, and winp have the same meaning as
     described for openpty().

RETURN VALUES    [Toc]    [Back]

     The openpty() function returns 0 on success, or -1 on failure.

     The forkpty() function returns -1 on failure, 0 in the slave process, and
     the process ID of the slave process in the parent process.

ERRORS    [Toc]    [Back]

     On failure, openpty() will set the global variable errno to ENOENT.

     In addition to this, forkpty() may set it to any value as described for
     fork(2).

SEE ALSO    [Toc]    [Back]

     chmod(2), chown(2), fork(2), getuid(2), open(2), revoke(2), login_tty(3),
     pty(4), termios(4), group(5)

BUGS    [Toc]    [Back]

     The calling process must have an effective UID of super-user in order to
     perform all the intended actions.	No notification will occur if
     openpty() or forkpty() failed to proceed with one of the described steps,
     as long as they could at least allocate the pty at all (and create the
     new process in the case of forkpty()).


FreeBSD 5.2.1		       December 29, 1996		 FreeBSD 5.2.1