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

       openpty, login_tty, forkpty - tty utility functions

       #include <pty.h>

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

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

       #include <utmp.h>

       int login_tty(int fd);

       Link with -lutil.

       The openpty() function finds an available pseudo-terminal 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-terminal 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
       pseudo-terminal.  The file descriptor of the master side of the pseudo-terminal 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 pseudo-terminal.

       If a call to openpty(), login_tty(), or forkpty() is not successful, -1 is returned and errno is set  to  indi-
       cate 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.

       openpty() will fail if:

       ENOENT There are no available ttys.

       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.

       These are BSD functions, present in libc5 and glibc2.

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

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

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

       This  page  is part of release 3.22 of the Linux man-pages project.  A description of the project, and informa-
       tion about reporting bugs, can be found at

GNU                               2003-07-18                        OPENPTY(3)