--- /dev/null
+#!/usr/bin/perl -w
+#
+# Copyright 2006 Ian Jackson <ijackson@chiark.greenend.org.uk>
+#
+# This script and its documentation (if any) are free software; you
+# can redistribute it and/or modify them under the terms of the GNU
+# General Public License as published by the Free Software Foundation;
+# either version 3, or (at your option) any later version.
+#
+# chiark-named-conf and its manpage are distributed in the hope that
+# it will be useful, but WITHOUT ANY WARRANTY; without even the
+# implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
+# PURPOSE. See the GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License along
+# with this program; if not, consult the Free Software Foundation's
+# website at www.fsf.org, or the GNU Project website at www.gnu.org.
+
+use strict;
+
+our $usage = <<'END';
+usage:
+ expire-iso8601 [<options>] <number>x<interval> [<number>x<interval> ...]
+options:
+ -u<unitlen> <interval> is measured in units of <unitlen> seconds
+ (default is 86400, so <interval> is in days)
+ -s<slop> allow kept items to be <slop> seconds shorter apart than
+ specified; default is 10% of <unitlen>
+ -n do not really delete
+ -r recursive removal (rm -r)
+example:
+ /home/ian/junk/expire-iso8601 14x1 4x7
+ uses units of 86400s (1 day) with a slop of 8640
+ it keeps 14 daily items
+ (that is 14 items, dated no less than 86400-8640 apart)
+ and 4 weekly items
+ (that is 4 items, dated no less than 7*86400-8640 apart)
+ the 14 daily and 7 weekly items may be the same, or not
+ There is no need to sort the list of <number>x<interval> pairs.
+exit status:
+ 0 ok
+ 4 rm failed
+ 8 bad usage
+ 16 catastrophic failure
+END
+
+use Carp;
+use DateTime::Format::ISO8601;
+
+our @files;
+our $rm = 1;
+our $recurse = 1;
+our $unit = 86400;
+our $slop;
+our @intervals;
+
+sub scan () {
+ my $parser = DateTime::Format::ISO8601->new;
+
+ foreach my $f (<[0-9]*>) {
+ if ($f !~ m/^ \d\d\d\d - \d\d - \d\d
+ (?: T \d\d \: \d\d (?: \: \d\d )?
+ (?: [-+] \d{1,2} \:? \d\d )? )? /x) {
+ print STDERR "ignoring $f\n";
+ }
+ my $t = $parser->parse_time($f) // confess;
+ my $t = $t->epoch() // confess;
+ push @files, { F => $f, T => $t, U => [] ];
+ }
+}
+
+sub precomp () {
+ if (!@files) {
+ print STDERR "none at all yet!\n";
+ exit 0;
+ }
+
+ # newest first, which means biggest T
+ @files = sort { $b->{T} <=> $a->{T} || $b->{F} cmp $a->{F} } @files;
+ my $newest_t = $files[0]{T};
+ $_->{A} = ($newest_t - $_->{T}) / $unit foreach @files;
+ $slop /= $unit;
+}
+
+sub flag ($) {
+ my ($int) = @_;
+ my $n = $int->{Number};
+ my $d = $int->{Interval};
+ my $spec = $int->{Spec};
+ my $start_age = $int->{Number+1) * $interval;
+ my $i = 0;
+
+ # find $i, the youngest which is at least $number x $interval
+ for (;;) {
+ last if $files[$i]{A} > $start_age;
+ if ($i == $#files) {
+ print STDERR "insufficient for $spec\n";
+ }
+ $i++;
+ }
+
+ for (;;) {
+ push $files[$i]{U}, $spec;
+
+ # find $j, the closest to $i which is at least $d-slop younger
+ my $j = $i;
+ for (;;) {
+ $j--;
+ last if $j < 0;
+ last if $files[$j];
+ my $dt = $files[$i]{A} - $files[$j]{A};
+ last if $dt >= $d - $slop;
+ }
+ last if $j < 0;
+
+ $i = $j;
+ }
+}
+
+sub implement () {
+ foreach (@files) {
+ next unless @{$_->{U}};
+ print "keep $_->{F} for @{$_->{U}}\n";
+ }
+ foreach (@files) {
+ next if @{$_->{U}};
+ print "remove $_>{F}\n";
+ if ($rm) {
+ my $r= system 'rm', ($recurse ? ('-r') : ()), "--", $_->{F};
+ die "run rm: $!\n" unless defined($r) && $r >= 0;
+ exit 16 if $r;
+ }
+ }
+}
+
+while (@ARGV && $ARGV[0] =~ m/^-/) {
+ $_ = shift @ARGV;
+ last if $_ eq '-' || $_ eq '--';
+ if (m/^-[^-]/) {
+ while (m/^-./) {
+ if (s/^-n/-/) { $rm=0; }
+ elsif (s/-r/-/) { $recurse=1; }
+ elsif (s/-u(\d+)$//) { $unit=$1; }
+ elsif (s/-s(\d+)$//) { $slop=$1; }
+ else { badusage "unknown short option $_" }
+ }
+ } elsif (m/^--help$/) {
+ print $usage or die $!;
+ exit 0;
+ } else {
+ badusage "unknown long option $_"
+ }
+}
+
+badusage "too few arguments" unless @ARGV;
+
+$slop //= $unit * 0.1;
+
+foreach (@ARGV) {
+ m/^(\d+)x(\d+)$/ or badusage "bad <number>x<interval> $_";
+ push @intervals, { Spec => $&, N => $1, I => $2 ];
+}
+
+scan();
+precomp();
+foreach $int (@intervals) { flag $int }
+implement();