#63 Keeping Track of the Weather

Another straightforward use of website scraping that illustrates yet a different approach is a weather forecast tool. Specify a zip code, and this script goes to the Census Bureau to obtain population and latitude/longitude information. It visits AccuWeather to extract the current weather in that region.

The Code

#!/bin/sh

# weather - Reports the weather forecast, including lat/long, for a zip code.

llurl="http://www.census.gov/cgi-bin/gazetteer?city=&state=&zip="
wxurl="http://wwwa.accuweather.com"
wxurl="$wxurl/adcbin/public/local_index_print.asp?zipcode="
if [ "$1" = "-a" ] ; then
  size=999; shift
else
  size=5
fi

if [ $# -eq 0 ] ; then
  echo "Usage: $0 [-a] zipcode" >&2
  exit 1
fi

if [ $size -eq 5 ] ; then
  echo ""

  # Get some information on the zip code from the Census Bureau

  lynx -source "${llurl}$1" | \
    sed -n '/^<li><strong>/,/^Location:/p' | \
    sed 's/<[^>]*>//g;s/^ //g'
fi

# The weather forecast itself at accuweather.com

lynx -source "${wxurl}$1" | \
  sed -n '/<font class="sevendayten">/,/[^[:digit:]]<\/font>/p' | \
  sed 's/<[^>]*>//g;s/^ [ ]*//g' | \
  uniq | \
  head -$size

exit 0

How It Works

This script provides yet another riff on the idea of using a shell script as a wrapper, though in this case the optional flag primarily changes the amount of information filtered through the head at the end of the pipe. This script also takes advantage of the natural source code organization of the two sites to slice out the population and latitude/longitude data prefixed with the strings <strong> and Location:, respectively, and then it slices out the forecast information wrapped in a sevendayten font container.

Running the Script

The standard way to invoke this script is to specify the desired zip code. If census information is available for that region, it'll be displayed, and the most recent weather forecast summary will be shown too. Add the -a flag, however, and it skips the census information and reports a full ten-day forecast.

The Results

$ weather 66207

Zip Code: 66207  PO Name: Shawnee Mission (KS)
Population (1990): 13863
Location: 38.957472 N, 94.645193 W

Currently at 10:35 PM
CLEAR    Winds SW  at 4 mph.
Temp: 28 / RF 26. UV Index 0.

A typical winter evening in Kansas: a warm 28 degrees Fahrenheit. Brrrrr.