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openpty(3)
NAME
  openpty, forkpty - Open and fork pseudoterminals

LIBRARY
  Standard C Library (libc.a)

SYNOPSIS
  #include <sys/termios.h>
	   <sys/ioctl.h>
  int openpty(
	  int *master,
	  int *slave,
	  char *name,
	  struct termios *termp,
	  struct winsize *winp);
  pid_t	 forkpty(
	  int *master,
	  char *name,
	  struct termios *termp,
	  struct winsize *winp);

PARAMETERS
  master    Points to the returned file descriptor for the master
	    pseudoterminal (pty).

  slave	    Points to the returned file descriptor for the slave pty.

  name	    Points to the pathname of the slave pty.  This parameter is
	    optional.

  termp	    Specifies the termios structure containing the terminal
	    attributes for the opened slave pty.  This parameter is optional.

  winp	    Specifies the winsize structure containing the window attributes
	    for the opened slave pty.  This parameter is optional.

DESCRIPTION
  The openpty() function opens the pty master/slave pair and sets the
  terminal attributes of the slave pseudoterminal according to the
  specifications in the termp and winp parameters.  The forkpty() function
  creates a child process and establishes the slave pty as the child process'
  controlling terminal.

				     Note
  If a signal handler for SIGCHLD exists and the openpty() or forkpty()
  function is invoked without superuser privileges, the signal handler must
  be able to dismiss an unexpected SIGCHLD signal.

RETURN VALUES
  Upon successful completion, the openpty() function returns a value of 0
  (zero).  Otherwise, it returns a value of -1.


  On success, the forkpty() function returns a value of 0 (zero) to the child
  process and returns the process ID of the child process to the parent
  process.  On error, the forkpty() function returns a value of -1 to the
  parent process and does not create a child process.

ERRORS
  If any of the following conditions occurs, the openpty() function sets
  errno to the corresponding value:

  [ENOENT]  The slave pty special files have been exhausted.

  [ENXIO]   No more ptys can be opened.	 The configured number of ptys has
	    been reached.

  [EMFILE]  The system limit for open file descriptors per process has
	    already reached OPEN_MAX.  The system limit for open file
	    descriptors has been reached.

	    [DIGITAL]  Either the OPEN_MAX value or the per-process soft
	    descriptor limit is checked.

  [ENFILE]  The system file table is full.

  [ENOMEM]  The system was unable to allocate kernel memory for more file
	    descriptors/processes.

  [EAGAIN]  The system-imposed limit on the total number of processes
	    executing for a single user has been exceeded.  This limit can be
	    exceeded by a process with superuser privilege.

RELATED INFORMATION
  Functions: fork(2)