Web scraping

Create a program that downloads the time from this URL: http://tycho.usno.navy.mil/cgi-bin/timer.pl and then prints the current UTC time by extracting just the UTC time from the web page's HTML.

Only use libraries that come at no extra monetary cost with the programming language and that are widely available and popular such as CPAN for Perl or Boost for C++.

AWK

This is inspired by GETURL example in the manual for gawk.

#! /usr/bin/awk -f

BEGIN {
  purl = "/inet/tcp/0/tycho.usno.navy.mil/80"
  ORS = RS = "\r\n\r\n"
  print "GET /cgi-bin/timer.pl HTTP/1.0" |& purl
  purl |& getline header
  while ( (purl |& getline ) > 0 )
  {
     split($0, a, "\n")
     for(i=1; i <= length(a); i++)
     {
        if ( a[i] ~ /UTC/ )
        {
          sub(/^<BR>/, "", a[i])
          printf "%s\n", a[i]
        }
     }
  }
  close(purl)
}

Bash

This solution uses curl, which can be downloaded for free (and very easily on GNU/Linux systems), and popular (at list in the GNU and *n*x world) utilities programs like grep and sed.

#! /bin/bash
curl -s http://tycho.usno.navy.mil/cgi-bin/timer.pl |
   grep 'UTC$' |
   sed -e 's/^<BR>//'

Java

<java>import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; import java.net.URL; import java.net.URLConnection;

public class WebTime{ public static void main(String[] args){ try{ URL address = new URL( "http://tycho.usno.navy.mil/cgi-bin/timer.pl"); URLConnection conn = address.openConnection(); BufferedReader in = new BufferedReader( new InputStreamReader(conn.getInputStream())); String line; while(!(line = in.readLine()).contains("UTC")); System.out.println(line.substring(4)); }catch(IOException e){ System.err.println("error connecting to server."); e.printStackTrace(); } } } </java>

OCaml

<ocaml>let () =

 let _,_, page_content = make_request ~url:Sys.argv.(1) ~kind:GET () in

 let lines = Str.split (Str.regexp "\n") page_content in
 let str =
   List.find
     (fun line ->
       try ignore(Str.search_forward (Str.regexp "UTC") line 0); true
       with Not_found -> false)
     lines
 in
 let str = Str.global_replace (Str.regexp "
") "" str in
 print_endline str;

</ocaml>

There are libraries for this, but it's rather interesting to see how to use a socket to achive this, so see the implementation of the above function make_request on this page.

Perl

<perl>use LWP::UserAgent;

my $url = 'http://tycho.usno.navy.mil/cgi-bin/timer.pl'; LWP::UserAgent->new->get($url)->content() =~ /
(.+? UTC)/

   and print "$1\n";</perl>

Python

<python>import urllib

page = urllib.urlopen('http://tycho.usno.navy.mil/cgi-bin/timer.pl') for line in page:

   if ' UTC\n' in line:
       print line.strip()[4:]
       break

page.close()</python> Sample output:

Aug. 20, 19:50:38 UTC

Ruby

require "open-uri"

open('http://tycho.usno.navy.mil/cgi-bin/timer.pl') do |p|

   p.each_line do |line|
     if line =~ /UTC\n/
       puts line[4,line.length]
       break
     end
   end

end