Found in chiark:/usr/local/lib/news/feed+read/getgroups.

diff --git a/newsrc-lg/getgroups b/newsrc-lg/getgroups
new file mode 100755 (executable)
index 0000000..52e995e
--- /dev/null
+++ b/newsrc-lg/getgroups
@@ -0,0 +1,67 @@
+#!/usr/bin/perl
+
+$minreaddays= 21;
+$maxperuser= 250;
+$fetchdir= "/var/lib/news/fetch";
+chdir("/etc/news") || die $!;
+
+open(CONF,"nntp-merge.conf") || die $!;
+while(<CONF>) {
+    next if m/^\#/ || !m/^\S/;
+    next if m/^(myfqdn|xref|server|server-nosearch|fetch|read|post|permit|believe|minreaddays)\s/;
+    if (m/^maxperuser\s+(\d+)\s+$/) {
+        $maxperuser= $1;
+    } elsif (m/^extrarc\s+(\S+)\s+$/) {
+        push(@extrarc,$1);
+    } else {
+        die "$_ ?";
+    }
+}
+
+open IGN,"</etc/news/newsrc-ignoredusers" or die $!;
+while (<IGN>) {
+    chomp;
+    next if m/^\#/;
+    s/\s*$//;
+    $ign{$_}= 1;
+}
+close IGN or die $!;
+
+open PASS,"</etc/userlist" or die $!;
+while (<PASS>) {
+    chomp;
+    next if m/^\#/;
+    $user= $_;
+    next if $ign{$user};
+    open GL,"userv -t 30 $user newsrc-listgroups |" or die $!;
+    scan("user $user",1);
+    close GL; $? and warn "getgroups: error getting groups for $user (code $?)";
+}
+close PASS or die $!;
+
+for $f (@extrarc) {
+    open GL,"< $f" or die $!;
+    scan("file $f",0);
+    close GL or die $!;
+}
+
+chdir($fetchdir) || die $!;
+open(NG,">all-read-groups.new") || die $!;
+print(NG join("\n",sort keys %yes)."\n") || die $!;
+close(NG) || die $!;
+rename("all-read-groups.new","all-read-groups") || die $!;
+
+printf "total %d groups\n",scalar(keys %yes);
+exit(0);
+
+sub scan ($) {
+    my ($where,$toomanyenf) = @_;
+    @g= ();
+    while (<GL>) {
+       die "bad group in $where" unless m/^[-a-z0-9+]+\.[-a-z0-9+._]+$/i;
+       push @g, $&;
+    }
+    warn("too many from $where"), return if $toomanyenf && @g > $maxperuser;
+    map { $yes{$_}=1; } @g;
+    printf "%-20s - %4d groups\n",$where,scalar(@g);
+}