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.

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
       This page is part of release 4.10 of the Linux  man-pages  project.   A
       description  of	the project, information about reporting bugs, and the
       latest	 version    of	  this	  page,	   can	   be	  found	    at
       https://www.kernel.org/doc/man-pages/.



GNU				  2015-04-19			    OPENPTY(3)