plotting sensor data with RRDtool

env_create.sh

# expected format
#{
#       "location": "92882",
#       "Air": 166,
#       "Carbon-Monoxide": 208,
#       "Hexane": 227,
#       "Methane": 253,
#       "Benzine": 245,
#       "Alcohol": 256,
#       "LPG": 274
#}
rrdtool create env.rrd \
  --step 60 \
  DS:Air:GAUGE:90:100:200 \
  DS:CarbonMonoxide:GAUGE:90:100:300 \
  DS:Hexane:GAUGE:90:100:300 \
  DS:Methane:GAUGE:90:100:300 \
  DS:Benzine:GAUGE:90:100:300 \
  DS:Alcohol:GAUGE:90:100:300 \
  DS:LPG:GAUGE:90:100:300 \
  RRA:MAX:0.5:1:2016

env_fetch.sh

# read mat's sensor data
# expected format
#{
#       "location": "92882",
#       "Air": 166,
#       "Carbon-Monoxide": 208,
#       "Hexane": 227,
#       "Methane": 253,
#       "Benzine": 245,
#       "Alcohol": 256,
#       "LPG": 274
#}
# join all numerical values of last 7 rows
wget -q -O - http://75.83.160.111:8085/env/ | grep -o '[0-9]\+' | tail -n 7 | paste -sd ':'

env_graph.sh

rrdtool graph /var/www/env.png \
  -w 785 -h 240 -a PNG \
  --start -86400 --end now \
  --vertical-label "value" \
  DEF:Air=/home/jdevoo/env.rrd:Air:MAX \
  DEF:CarbonMonoxide=/home/jdevoo/env.rrd:CarbonMonoxide:MAX \
  DEF:Hexane=/home/jdevoo/env.rrd:Hexane:MAX \
  DEF:Methane=/home/jdevoo/env.rrd:Methane:MAX \
  DEF:Benzine=/home/jdevoo/env.rrd:Benzine:MAX \
  DEF:Alcohol=/home/jdevoo/env.rrd:Alcohol:MAX \
  DEF:LPG=/home/jdevoo/env.rrd:LPG:MAX \
  LINE1:Air#ff0000:"Air" \
  LINE2:CarbonMonoxide#00ff00:"Carbon-Monoxide" \
  LINE1:Hexane#0000ff:"Hexane" \
  LINE1:Methane#0fa000:"Methane" \
  LINE1:Benzine#00fa00:"Benzine" \
  LINE1:Alcohol#000fa0:"Alcohol" \
  LINE1:LPG#f000f0:"LPG" \