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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  con-
       trolling  terminal  for the calling process, setting fd to be the stan-
       dard input, output, and error streams of the current process, and clos-
       ing fd.
       The  forkpty() function combines openpty(), fork(2), and login_tty() to
       create a new process operating in a pseudoterminal.  The file  descrip-
       tor  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)