Conky and noaa weather from xml

Question

i am looking into trying to retrieve weather data from noaa xml file for locations then displaying it in conky. i am having trouble just extracting the data i want without downloading the xml file to the computer let alone getting it to appear in conky.
i have tried wget | grep but all that happens is the file gets downloaded and grep part does nothing.
can someone point me in the right direction  that may help me
thanks.

Answer 1

I really don't know where I learned all this, mostly just google over time.
I believe that the weather station you are using is from La Guardia airport which is KLGA.
You can perhaps find a better station here.
Below is a script you may modify to suit your needs.
A little information about the script.  It uses wget to download the file into in /tmp/weather. On Arch Linux, /tmp is not actually on disk, but is in shared memory.  Thus the .xml file will be downloaded into shared memory.
Since it appears that the weather data is updated once per hour (as near as I can tell), the script will not try to retrieve new data until at least one hour and 15 minutes after the last observed time.  (I chose 1:15 since at La Guardia at least, there is about a 11 minute delay between when they make a weather observation and put the data online.) If the new data is still old (which could happen if the weather station is having problems or maintenence, etc.) then the script will keep trying to get new data roughly once every five minutes until the station comes back on line.
The script takes the weather station (KLGA for instance) as a command line parameter so you could easily use a different station.
#!/bin/bash
station="$1.xml"
wdir='/tmp/weather'
update_xml() {
if [ ! -e "$station" ]; then
wget -q http://w1.weather.gov/xml/current_obs/${station}
[ -e "$station" ] && touch "${station}"
else
# dtime: time the .xml file was downloaded
# otime: time the weather data was observed
# ctime: current time (time this script is being run)
dtime=$(stat -c %Y $station)
otime=$(date -d "$utime" +%s)
ctime=$(date +%s)
if (( "$otime" + 4507 < "$ctime" )); then
if (( "$dtime" + 307 < "$ctime" )); then
wget -q -O "$station" http://w1.weather.gov/xml/current_obs/${station}
[ -e "$station" ] && touch "${station}"
fi
fi
fi
from_xml() { xmllint -xpath "//$1" - <<< "$xml" | sed 's/<[^>]*>//g'; }
[ -d "$wdir" ] || mkdir -p "$wdir"
cd "$wdir" || exit 1
xml=''
[ -r $station ] && xml="$(< $station)"
( update_xml >/dev/null 2>&1 ) &
if [ -n "$xml" ]; then
location=$(from_xml "location")
utime=$(from_xml "observation_time_rfc822")
weather=$(from_xml "weather")
temperature=$(from_xml "temp_f")
humid=$(from_xml "relative_humidity")
wind_dir=$(from_xml "wind_dir")
case "$wind_dir" in
"North") wind_dir="N" ;;
"South") wind_dir="S" ;;
"East") wind_dir="E" ;;
"West") wind_dir="W" ;;
"Northwest") wind_dir="NW" ;;
"Northeast") wind_dir="NE" ;;
"Southwest") wind_dir="SW" ;;
"Southeast") wind_dir="SE" ;;
esac
wind_speed=$(from_xml "wind_kt")
baro_pressure=$(from_xml "pressure_in")
echo "$location"
echo "Updated: $(date -d "$utime" 2>/dev/null )"
printf 'Weather: %s %s°F\n' "$weather" "$temperature"
printf 'Barometric Pressure: %s inches\n' "$baro_pressure"
printf 'Wind: %s at %s knots\n' "$wind_dir" "$wind_speed"
printf 'Humidity: %s%%\n' "$humid"
else
echo "No weather data available."
fi
Then in your .conkyrc do (don't forget the KLGA):
${exec /path/to/script KLGA}
Finally, I see that there are also a set of thumbnail images that NOAA provides that coorespond to the current weather conditions. As conky is capable of displaying these thumbnails, you could set up conky to do that as well.  It is a little more involved, so let me know if you are interested.