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Linux 2.6 - man page for posix_openpt (linux section 3posix)

POSIX_OPENPT(P) 		    POSIX Programmer's Manual			  POSIX_OPENPT(P)

       posix_openpt - open a pseudo-terminal device

       #include <stdlib.h>
       #include <fcntl.h>

       int posix_openpt(int oflag);

       The  posix_openpt()  function  shall  establish a connection between a master device for a
       pseudo-terminal and a file descriptor. The file descriptor is used by other I/O	functions
       that refer to that pseudo-terminal.

       The  file  status  flags  and  file access modes of the open file description shall be set
       according to the value of oflag.

       Values for oflag are constructed by a bitwise-inclusive OR of  flags  from  the	following
       list, defined in <fcntl.h>:

       O_RDWR Open for reading and writing.

	      If set posix_openpt() shall not cause the terminal device to become the controlling
	      terminal for the process.

       The behavior of other values for the oflag argument is unspecified.

       Upon successful completion, the posix_openpt() function shall open a master  pseudo-termi-
       nal  device and return a non-negative integer representing the lowest numbered unused file
       descriptor. Otherwise, -1 shall be returned and errno set to indicate the error.

       The posix_openpt() function shall fail if:

       EMFILE {OPEN_MAX} file descriptors are currently open in the calling process.

       ENFILE The maximum allowable number of files is currently open in the system.

       The posix_openpt() function may fail if:

       EINVAL The value of oflag is not valid.

       EAGAIN Out of pseudo-terminal resources.

       ENOSR  Out of STREAMS resources.

       The following sections are informative.

   Opening a Pseudo-Terminal and Returning the Name of the Slave
       Device and a File Descriptor

	      #include <fcntl.h>
	      #include <stdio.h>

	      int masterfd, slavefd;
	      char *slavedevice;

	      masterfd = posix_openpt(O_RDWR|O_NOCTTY);

	      if (masterfd == -1
		  || grantpt (masterfd) == -1
		  || unlockpt (masterfd) == -1
		  || (slavedevice = ptsname (masterfd)) == NULL)
		  return -1;

	      printf("slave device is: %s\n", slavedevice);

	      slavefd = open(slave, O_RDWR|O_NOCTTY);
	      if (slavefd < 0)
		  return -1;

       This function is a method for portably obtaining a file descriptor of  a  master  terminal
       device for a pseudo-terminal. The grantpt() and ptsname() functions can be used to manipu-
       late mode and ownership permissions, and to obtain the name of the slave  device,  respec-

       The  standard developers considered the matter of adding a special device for cloning mas-
       ter pseudo-terminals: the /dev/ptmx device. However, consensus could not be  reached,  and
       it  was	felt  that  adding  a  new  function  would  permit  other  implementations.  The
       posix_openpt() function is designed to complement the grantpt(), ptsname(), and unlockpt()

       On  implementations  supporting the /dev/ptmx clone device, opening the master device of a
       pseudo-terminal is simply:

	      mfdp = open("/dev/ptmx", oflag );
	      if (mfdp < 0)
		  return -1;


       grantpt()  ,  open()  ,	ptsname()  ,  unlockpt()  ,  the  Base	Definitions   volume   of
       IEEE Std 1003.1-2001, <fcntl.h>

       Portions  of  this  text  are  reprinted  and  reproduced in electronic form from IEEE Std
       1003.1, 2003 Edition, Standard for Information Technology  --  Portable	Operating  System
       Interface  (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by
       the Institute of Electrical and Electronics Engineers, Inc and  The  Open  Group.  In  the
       event  of  any  discrepancy  between this version and the original IEEE and The Open Group
       Standard, the original IEEE and The Open Group Standard is the referee document. The orig-
       inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group			       2003				  POSIX_OPENPT(P)

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