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 messages 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 message 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 system.

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)