Web scraping

Web scraping
You are encouraged to solve this task according to the task description, using any language you may know.

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.

If possible, 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)
}

C

Works with: POSIX version .1-2001

Library: libcurl

There's no any proper error handling.

<lang c>#include <stdio.h>

1. include <string.h>
2. include <curl/curl.h>
3. include <sys/types.h>
4. include <regex.h>

1. define BUFSIZE 16384

size_t lr = 0;

size_t filterit(void *ptr, size_t size, size_t nmemb, void *stream) {

 if ( (lr + size*nmemb) > BUFSIZE ) return BUFSIZE;
 memcpy(stream+lr, ptr, size*nmemb);
 lr += size*nmemb;
 return size*nmemb;

}

int main() {

 CURL *curlHandle;
 char buffer[BUFSIZE];
 regmatch_t amatch;
 regex_t cregex;

 curlHandle = curl_easy_init();
 curl_easy_setopt(curlHandle, CURLOPT_URL, "http://tycho.usno.navy.mil/cgi-bin/timer.pl");
 curl_easy_setopt(curlHandle, CURLOPT_FOLLOWLOCATION, 1);
 curl_easy_setopt(curlHandle, CURLOPT_WRITEFUNCTION, filterit);
 curl_easy_setopt(curlHandle, CURLOPT_WRITEDATA, buffer);
 int success = curl_easy_perform(curlHandle);
 curl_easy_cleanup(curlHandle);

 buffer[lr] = 0;
 
 regcomp(&cregex, "UTC$", REG_NEWLINE);
 regexec(&cregex, buffer, 1, &amatch, 0);
 int bi = amatch.rm_so;
 while ( bi-- > 0 )
   if ( memcmp(&buffer[bi], "
", 4) == 0 ) break;

 buffer[amatch.rm_eo] = 0;

 printf("%s\n", &buffer[bi+4]);

 regfree(&cregex);
 return 0;

}</lang>

E

<lang e>interp.waitAtTop(when (def html := <http://tycho.usno.navy.mil/cgi-bin/timer.pl>.getText()) -> {

   def rx`(?s).*>(@time.*? UTC).*` := html
   println(time)

})</lang>

Java

<lang 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(); } } } </lang>

OCaml

<lang 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;

</lang>

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

Perl

<lang perl>use LWP::Simple;

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

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

Python

<lang 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()</lang> Sample output:

Aug. 20, 19:50:38 UTC

Ruby

<lang 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..-1]
       break
     end
   end

end</lang>

Tcl

<lang tcl> package require http

set request [http::geturl "http://tycho.usno.navy.mil/cgi-bin/timer.pl"] if {[regexp {
(.* UTC)} [http::data $request] --> utc]} {

   puts $utc

} </lang>

UNIX Shell

Works with: Bourne Again SHell

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>//'