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 ter‐
       minal 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 call‐
       ing process.

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

CONFORMING TO
       These are BSD functions, present in glibc.  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 pseu‐
       doterminal 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 3.74 of the Linux man-pages project.  A  description  of  the
       project,  information  about  reporting  bugs, and the latest version of this page, can be
       found at http://www.kernel.org/doc/man-pages/.



GNU                                         2014-08-19                                 OPENPTY(3)