ultrix 2.0 _iob storage

[Jon Wells]

G'day,

Just wondering how _iob in declared in real unix systems 
(ones that dec hasn't got at).

I found a piece of code in Kyoto Common Lisp which does....

    ..
nfiles = getdtablesize();
for ( p = &_iob[3]; p < _iob[nfiles]; p++ )
	fclose(p);
    ..

Eg. charges though _iob trying to close any stream that's open
 (apart from stdin/stdout/stderr).

You can't do this with ultrix (2.0) as _iob is only 3 slots long, all
other struct _iobuf's are allocated dynamically so &_iob[3]....
just points off into the weeds.

Is the above code deemed to be a reasonable way of doing this?

Ultrix provides a function called _fwalk() which, given a pointer to a
function, will call that function for every open stream passing it the
FILE *.

It's totally undocumented, I grep'd through every manual entry looking
for it (I found it by tracing exit(), it's name looked interresting in
nm's output).

Is _fwalk() standard on other genders of unix???
Does every one else store all the _iobuf's in _iob as one array?
Is this another dec knows best????
Or is there a much better way of closing everything but stdin etc.????

jon
--