login_tty

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



NAME
       openpty, login_tty, forkpty - tty utility functions

SYNOPSIS
       #include <pty.h>	 /* for openpty and forkpty */
       #include <utmp.h> /* for login_tty */

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

       int login_tty(int fd);

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

DESCRIPTION
       The  openpty() function finds an available pseudo-tty 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 tty fd (which may
       be  a  real  tty	 device,  or the slave of a pseudo-tty as returned by
       openpty()) by creating a new session, making fd the controlling termi-
       nal for the current process, setting fd to be the standard input, out-
       put, and error streams of the current process, and closing fd.

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

RETURN VALUES
       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 ttys.

       login_pty()  will  fail	if ioctl() fails to set fd to the controlling
       terminal of the current process.

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

NOTE
       These functions are included in libutil,	 hence	you’ll	need  to  add
       -lutil to your compiler commandline.

FILES
       /dev/[pt]ty[pqrstuwxyzabcdePQRST][0123456789abcdef]

CONFORMING TO
       These are BSD functions, present in libc5 and glibc2.

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)



BSD				  2003-07-18			   OPENPTY(3)