>From the keyboard of fuat@news.ans.net (Fuat C. Baran):
:Is there a way to store file descriptors (from an open()) in an array?
:I would like to open a set of files, store the open file descriptors
:in an associative array keyed by filename and be able to multiplex
:output to one of the files in a loop where for each line of output I'm
:given a filename.  I'd like to check if $filehandles{$filename} is
:defined and if not first open the file.

Here's one thing that I use.  Just call
    
    &'cachein($filename);

and now you can say

    while (<$filename>) {
	
    } 


It also gives nice error message for warn and die this way.
Here are the routines; beware that Suns lies about what NOFILE
really is.  Thanks for helping us write portable code, Sun.

--tom

    sub init_filecache {
	package filecache;

	if (defined &'NOFILE) {
	    $maxopen = &'NOFILE - 12;
	    return;
	} 

	$seq = 0;
	$numopen = 0;

	if (open(PARAM,'/usr/include/sys/param.h')) {
	    local($.);
	    while (<PARAM>) {
		$maxopen = $1 - 12 if /^\s*#\s*define\s+NOFILE\s+(\d+)/;
		$'NOFILE = $1;
	    }
	    close PARAM;
	}
	$maxopen = 6 unless $maxopen;
    } 


    sub filecache'open {
    # open in their package
	open($_[0], $_[1]);
    } 
    # but they only get to see this one

    sub main'cachein {
	package filecache;
	($file) = @_;
	($package) = caller;
	if (!$isopen{$file}) {
	    if (++$numopen > $maxopen) {
		sub byseq {$isopen{$a} <=> $isopen{$b};}
		local(@lru) = sort byseq keys(%isopen);
		splice(@lru, $maxopen / 3);
		$numopen -= @lru;
		for (@lru) { close $_; delete $isopen{$_}; }
	    }
	    &open($file, "< " . $file) || return undef;
	} elsif ($'U{'debug'}) {
	    # 
	} 
	seek($file,0,0);
	$isopen{$file} = ++$seq;
    } 

    sub main'uncache {
	package filecache;
	local($file);
	for $file (@_) {
	    if ($isopen{$file}) {
		close $file;
		delete $isopen{$file};
		$numopen--;
	    } 
	} 
    } 

    sub main'clear_filecache { # (DIRECTORY)
    #%%#
    #%%# Close anything cached open in this directory.
    #%%#
	package filecache;
	local($dir) = @_;
	for $file (keys %isopen) {
	    if (index($file,$dir) == 0 && 
		substr($file, length($dir), 1) eq '/')
	    {
		close $file;
		delete $isopen{$file};
		$numopen--;
	    } 
	} 
    } 

__END__
-- 
    Tom Christiansen      tchrist@convex.com      convex!tchrist

    echo "Your stdio isn't very std."
            --Larry Wall in Configure from the perl distribution



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