OPENPTY(3)						     Linux Programmer's Manual							OPENPTY(3)

NAME

       openpty, login_tty, forkpty - terminal utility functions

SYNOPSIS

       #include <pty.h>

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

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

       #include <utmp.h>

       int login_tty(int fd);

       Link with -lutil.

DESCRIPTION

       The  openpty()  function finds an available pseudoterminal and returns file descriptors for the master and slave in amaster and aslave.	If
       name is not NULL, the filename of the slave is returned in name.  If termp is not NULL, the terminal parameters of the slave will be set to
       the values in termp.  If winp is not NULL, the window size of the slave will be set to the values in winp.

       The  login_tty() function prepares for a login on the terminal fd (which may be a real terminal device, or the slave of a pseudoterminal as
       returned by openpty()) by creating a new session, making fd the controlling terminal for the calling process, setting fd to be the standard
       input, output, and error streams of the current process, and closing fd.

       The  forkpty()  function  combines  openpty(),  fork(2),  and  login_tty() to create a new process operating in a pseudoterminal.  The file
       descriptor of the master side of the pseudoterminal is returned in amaster, and the filename of the slave in name if it is not  NULL.   The
       termp and winp arguments, if not NULL, will determine the terminal attributes and window size of the slave side of the pseudoterminal.

RETURN VALUE

       If  a  call  to	openpty(), login_tty(), or forkpty() is not successful, -1 is returned and errno is set to indicate the error.	Otherwise,
       openpty(), login_tty(), and the child process of forkpty() return 0, and the parent process of forkpty() returns  the  process  ID  of  the
       child process.

ERRORS

       openpty() will fail if:

       ENOENT There are no available terminals.

       login_tty() will fail if ioctl(2) fails to set fd to the controlling terminal of the calling process.

       forkpty() will fail if either openpty() or fork(2) fails.

CONFORMING TO

       These are BSD functions, present in libc5 and glibc2.  They are not standardized in POSIX.

NOTES

       The const modifiers were added to the structure pointer arguments of openpty() and forkpty() in glibc 2.8.

       In versions of glibc before 2.0.92, openpty() returns file descriptors for a BSD pseudoterminal pair; since glibc 2.0.92, it first attempts
       to open a UNIX 98 pseudoterminal pair, and falls back to opening a BSD pseudoterminal pair if that fails.

BUGS

       Nobody knows how much space should be reserved for name.  So, calling openpty() or forkpty() with non-NULL name may not be secure.

SEE ALSO

       fork(2), ttyname(3), pty(7)

COLOPHON

       This page is part of release 3.53 of the Linux man-pages project.  A description of the project, and information about reporting bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.

GNU
								    2010-06-13								OPENPTY(3)