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Date:	Tue, 29 Sep 1992 10:38:04 -0400
From:	rsalz@osf.org
Message-Id: <9209291438.AA22337@earth.osf.org>
To:	byron@netapp.com, rc@hawkwind.utcs.toronto.edu
Subject: Re:  recent rc hacks

I like Byron's idea, but I like even more the idea of not needing these
little scripts or programs lying around.  And even more perversely, I like
the idea of using big monstrous perl to tame the history of small elegant
rc.  So, the following 45-line perl script.  It uses $histlog to say
where to write the history log file.

I don't know why but if I invoked this directly then my shell stopped
adding to the history (actually, I do sort of know why; I'd calll it a bug)
Using this function helps:
	fn trimhist { perl $h/bin/trimhist && history=$history }

#! /usr/bin/perl --

$size = 50;

$history = $ENV{'history'}
    || die "No \$history environment variable, stopped";
$old = $history . '~';
rename($history, $old) || die "Can't rename $!, stopped";
open(IN, $old) || die "Can't open $old $!, stopped";

##  Parse $history, filling in @lines with last unique occurence of each
##  command.
%commands = ();
@lines = ();
$count = 0;
line: while ( <IN> ) {
    chop;
    next line if /^-/ || /^; / || /^$/;
    $lines[$commands{$_}] = "" if defined $commands{$_};
    $commands{$_} = $count++;
    push(@lines, $_);
}
close(IN) || die "Can't close $history $!, stopped";
@lines = grep($_ ne "", @lines);

##  Open new output
open(OUT, ">$history") || die "Can't open $history $!, stopped";

##  Print last "$count" lines.
$start = $#lines - $size;
$start = 0 if $start < 0;
$count = 0;
foreach ( @lines[$start .. $#lines] ) {
    print OUT $_, "\n";
    $count++;
}
close(OUT) || die "Can't close $history $!, stopped";
unlink($old) || die "Can't remove $old $!, stopped";

##  Update $histlog (unset it to not do that).
$log = $ENV{'histlog'} || exit(0);
open(OUT, ">>$log") || die "Can't open $log $!, stopped";
($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst) = localtime(time);
printf OUT "%4d/%2.2d/%2.2d %d\n", $year + 1900, $mon + 1, $mday, $count;
close(OUT) || die "Can't close $log $!, stopped";