collectd script to report ipt hashtable sizes

collectd.conf

<Plugin exec>
  Exec "nobody" "/usr/local/bin/collectd_ipt_hashtable.sh"
</Plugin>

collectd_ipt_hashtable.sh

#!/bin/sh

HOSTNAME="${COLLECTD_HOSTNAME:-localhost}"
INTERVAL="${COLLECTD_INTERVAL:-60}"

cd /proc/net
while sleep "$INTERVAL"; do
    wc -l ip{6t,t}_hashlimit/* 2>/dev/null | while read count filename ; do
        metric=""
        case "$filename" in
            total)
                continue
                ;;
            ip6*)
                metric="ipv6-${filename##*/}"
                ;;
            ipt*)
                metric="ipv4-${filename##*/}"
                ;;
        esac
        echo "PUTVAL \"$HOSTNAME/ipt_hashlimit_count/gauge-$metric\" interval=$INTERVAL N:$count"
    done
done