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



NAME
       openpty, login_tty, forkpty - tty 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 pseudo-terminal and returns file descriptors for the master and slave in amas-
       ter 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-termi-
       nal.  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.

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 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.

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 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.

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 3.25 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)