wx.pl

#!/usr/bin/perl

use strict;
use warnings;
use LWP::Simple;

# Variables for temperature, humidity, wind direction, speed, gust and pressure
my $temperature;
my $humidity;
my $winddirection;
my $windspeed;
my $windgust;
my $pressure;

# RegEx match count
my $count;

# Convert month into 2 digit format
my $month = sprintf("%02d", ((localtime)[4] + 1) % 100);

# Convert day into 2 digit format
my $day = sprintf("%02d", (localtime)[3] % 100);

# Convert hour into 2 digit format
my $hour = sprintf("%02d", (localtime)[2] % 100);

# Convert minute into 2 digit format
my $minute = sprintf("%02d", (localtime)[1] % 100);

# URL of Regional Weather in Hong Kong (updates every 10 minutes)
my $html = get("http://data.weather.gov.hk/wxinfo/ts/text_readings_e.htm");

# Check if the page was loaded successfully and with right content
if (($html) && (index($html, "Regional Weather in Hong Kong") > -1)) {
	# Extract temperature (3 bytes)
	$count = () = $html =~ m{Shau Kei Wan[ ]+([\d\.?]+)};
	if ($count > 0) {
		$temperature = sprintf("%03d", ($1 * 9/5 + 32) % 1000);
	} else {
		$temperature = "...";
	}

	# Extract humidity (2 bytes)
	$count = () = $html =~ m{HK Observatory[ ]+[\S]+[ ]+([\d]+)};
	if ($count > 0) {
		$humidity = sprintf("%02d", $1 % 100);
	} else {
		$humidity = "..";
	}

	# Extract wind direction (3 bytes)
	my $pattern = "(km/hour)";
	my $offset = index($html, $pattern) + length($pattern) + 1;
	$html = substr($html, $offset);
	$count = () = $html =~ m{Kai Tak[ ]+([^\s]+)};
	if ($count > 0) {
		if (lc $1 eq "north")		{ $winddirection = "000"; }
		elsif (lc $1 eq "northeast")	{ $winddirection = "045"; }
		elsif (lc $1 eq "east")		{ $winddirection = "090"; }
		elsif (lc $1 eq "southeast")	{ $winddirection = "135"; }
		elsif (lc $1 eq "south")		{ $winddirection = "180"; }
		elsif (lc $1 eq "southwest")	{ $winddirection = "225"; }
		elsif (lc $1 eq "west")		{ $winddirection = "270"; }
		elsif (lc $1 eq "northwest")	{ $winddirection = "315"; }
		elsif (lc $1 eq "variable")	{ $winddirection = "..."; }
		else {	# When wind direction is either "Calm" or "N/A"
			$winddirection	= "...";
			$windspeed	= "...";
			$windgust	= "...";
		}
	} else {
		$winddirection	= "...";
		$windspeed	= "...";
		$windgust	= "...";
	}

	if ((!defined $windspeed) || (!defined $windgust)){
		# Extract wind speed (3 bytes)
		$count = () = $html =~ m{Kai Tak[ ]+[\S]+[ ]+([\d]+)};
		if ($count > 0) {
			$windspeed = sprintf("%03d", $1 * 0.621371192 % 1000);
		} else {
			$windspeed = "...";
		}
		# Extract wind gust (3 bytes)
		$count = () = $html =~ m{Kai Tak[ ]+[\S]+[ ]+[\S]+[ ]+([\d]+)};
		if ($count > 0) {
			$windgust = sprintf("%03d", $1 * 0.621371192 % 1000);
		} else {
			$windgust = "...";
		}
	}

	# Extract pressure (5 bytes)
	$pattern = "(hPa)";
	$offset = index($html, $pattern) + length($pattern) + 1;
	$html = substr($html, $offset);
	$count = () = $html =~ m{HK Observatory[ ]+([\d\.?]+)};
	if ($count > 0) {
		$pressure = sprintf("%05d", $1 * 10 % 100000);
	} else {
		$pressure = ".....";
	}

	# Output weather in the formation _MMDDHHMMcCCCsSSSgGGGtTTThHHbBBBBB
	print "_" . $month . $day . $hour . $minute . "c" . $winddirection . "s" . $windspeed . "g" . $windgust . "t" . $temperature . "h" . $humidity . "b" . $pressure;
} else {
	# Return blank values when there is problem loading URL
	print "_" . $month . $day . $hour . $minute . "c...s...g...t...h..b.....";
}