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
       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.
       If name is not NULL, the buffer it points to is used to return the filename of the slave.  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() fails if:

       ENOENT There are no available terminals.

       login_tty() fails if ioctl(2) fails to set fd to the controlling terminal of the calling process.

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

ATTRIBUTES

       For an explanation of the terms used in this section, see attributes(7).
       ┌──────────────────────┬───────────────┬────────────────────────┐
       │ Interface            │ Attribute     │ Value                  │
       ├──────────────────────┼───────────────┼────────────────────────┤
       │ forkpty(), openpty() │ Thread safety │ MT-Safe locale         │
       ├──────────────────────┼───────────────┼────────────────────────┤
       │ login_tty()          │ Thread safety │ MT-Unsafe race:ttyname │
       └──────────────────────┴───────────────┴────────────────────────┘

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 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

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       information   about   reporting   bugs,   and   the  latest  version  of  this  page,  can  be  found  at
       https://www.kernel.org/doc/man-pages/.

GNU                                                2017-09-15                                         OPENPTY(3)