Skip site navigation (1)Skip section navigation (2)

FreeBSD Manual Pages

  
 
  

home | help
GETFDS(3PVM)			PVM Version 3.4			  GETFDS(3PVM)

NAME
       pvm_getfds - Get	file descriptors in use	by PVM.

SYNOPSIS
       C    int	nfds = pvm_getfds( int **fds )

       Fortran	 Not Available

PARAMETERS
       fds     Returns integer array of	file descriptors.

DESCRIPTION
       A  PVM  task uses sockets to communicate	between	libpvm and other tasks
       or the pvmd.  It	is sometimes useful to know the	file  descriptor  num-
       bers  of	 the  sockets in order to wait from input from either PVM mes-
       sages or	an external source.  For example, the  PVM  console  waits  on
       both  keyboard  input and notify	messages.  Input can be	multiplexed by
       polling all sources, but	this wastes cpu	cycles.	 Instead, the select()
       system  call can	be used	to wait	until one or more sources of input are
       ready.

       If it completes successfully, pvm_getfds	returns	the number of  sockets
       in  use,	 and  the  file	 descriptor numbers in an array	(allocated and
       freed by	libpvm).  At least one socket  always  exists  (from  task  to
       pvmd),  and  its	 descriptor  is	 always	fds[0].	 The number of sockets
       varies as direct	routes are established to other	tasks.

       It can be difficult to track the	set  of	 file  descriptors  if	direct
       routing	is  enabled, because routes are	created	as messages are	either
       sent or received.  The simplest approach	is to disable direct routing.

       When select returns with	a PVM file descriptor ready, a	complete  mes-
       sage  may  be  ready  to	be received, or	instead	only a fragment	may be
       waiting.	 pvm_nrecv or pvm_probe	should be used test without blocking.

RESTRICTIONS
       pvm_getfds is only available when running PVM on	a Unix or similar sys-
       tem.

EXAMPLES
       The  following  program	fragment  waits	until either keyboard input is
       available, or a PVM message has arrived.

	    int	*d;
	    fd_set r;

	    pvm_setopt(PvmRoute, PvmDontRoute);
	    pvm_getfds(&d);

	    FD_ZERO(&r);
	    FD_SET(0, &r);
	    FD_SET(d[0], &r);
	    while (1) {
		 if (select(d[0] + 1, &r, (fd_set*)0, (fd_set*)0,
			    (struct timeval*)0)	> 0) {
		      if (FD_ISSET(0, &r))
			   ...	  /* read keyboard input */
		      if (FD_ISSET(d[0], &r) &&	pvm_nrecv(-1, -1) > 0)
			   ...	  /* got a PVM message */
		 }
	    }

ERRORS
       The following error condition can be returned by	pvm_getfds:

       PvmSysErr
	      pvmd not responding.

SEE ALSO
       pvm_notify(3PVM), pvm_trecv(3PVM)

				 22 Nov, 1994			  GETFDS(3PVM)

NAME | SYNOPSIS | PARAMETERS | DESCRIPTION | RESTRICTIONS | EXAMPLES | ERRORS | SEE ALSO

Want to link to this manual page? Use this URL:
<https://www.freebsd.org/cgi/man.cgi?query=pvm_getfds&sektion=3&manpath=FreeBSD+13.0-RELEASE+and+Ports>

home | help