• NAME
  
  openpty, login_tty, forkpty - tty utility functions
• SYNOPSIS
  

  
   #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.
  
  
  

• DESCRIPTION
  
  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.
  
• 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.
  
• NOTES
  
  
  
  
  
  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 3.19 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/.
  

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