Count flipdot's Freifunk clients

#!/bin/bash
# Count users currently logged into a list of Freifunk Kassel nodes

url_base=https://graphite.freifunk-kassel.de
url_params="rawData=true"

time_offset="5min"

node_pre="ffks.nodes."
node_post=".clients"
declare -a node_ids=(ffks-Flipdot flipdot-offloader liberation-box calden-test-a00 calden-test-a07 calden-test-a11 calden-test-a14)

nodes=""
for n in ${node_ids[@]}; do
    nodes="$nodes$node_pre$n$node_post,"
done
nodes="$(echo $nodes| rev | cut -c2- | rev)"

target_pre="sum("
target_post=")"
target="$target_pre$nodes$target_post)"

url="$url_base/render/?$url_params&target=$target&from=now-$time_offset&to=now"

echo "URL: $url"
n=$(curl -k "$url" | awk -F \| '{print $2}' | awk -F\, '{print $NF}')

if [[ "$n" == "None" ]]; then
    n=0
else
    n=${n/.*}
fi

echo $n