Beefy Boxes and Bandwidth Generously Provided by pair Networks
laziness, impatience, and hubris
 
PerlMonks  

Detect Broken links

by vishi83 (Pilgrim)
on Oct 15, 2009 at 07:56 UTC ( #801302=perlquestion: print w/ replies, xml ) Need Help??
vishi83 has asked for the wisdom of the Perl Monks concerning the following question:

Hi Perlmonks,

I want to detect broken links by running through a site with a script in perl. Which module can i use for doing this. Need help.

Thanks,
Vishy
A perl Script without 'strict' is like a House without Roof; Both are not Safe;

Comment on Detect Broken links
Re: Detect Broken links
by marto (Chancellor) on Oct 15, 2009 at 08:19 UTC
Re: Detect Broken links
by hawtin (Prior) on Oct 15, 2009 at 08:36 UTC

    I have a very old script that I do that with, it uses LWP to fetch the pages and parses the html with regex (yes, I know better now, but it works).

    At the time I failed to identify any module to do what I, needed and later I added various bits and pieces to count words, list external links and so on. So rolling my own turned out to be the best way to go. Essentially it was:

    use strict; use LWP::UserAgent; use IO::File; my $ua = LWP::UserAgent->new; $ua->agent("Angler/0.1 "); my $server_root = "/"; my %pages = ( $server_root => "needs_scan", # Note some pages that we don't want to visit "${server_root}login.htm" => "done", "${server_root}logout" => "done", "${server_root}table.xls" => "done", "${server_root}select_view" => "done", "${server_root}sws/error" => "done", ); my $default_host = "127.0.0.1"; my $default_port; my $done_some = 1; while($done_some) { $done_some = 0; foreach my $path (keys %pages) { next if($pages{$path} eq "done"); scan_page($path); $pages{$path} = "done"; $done_some = 1; $total_done++; if(($total_done % 1000) == 0) { print "\rDone $total_done"; } } } print "\nDone $total_done pages\n"; # A whole load of reporting in here exit 0; sub sub scan_page { my($path) = @_; print STDERR "Scanning: $path\n" if($verbose); if(!defined $base_name) { $base_name = "http://$default_host"; $base_name .= ":" . $default_port if($default_port != 80); } # Dir contains the relative path to the page so that # we can correctly adjust relative links $dir = $path; if($dir =~ s#/+[^/]*$#/#) { } else { $dir = $server_root; } %known_content_types = ( # Here are the link types that we know about at the start "text/html" => "HTML", "image/gif" => "ignore", "application/octet-stream" => "ignore", "application/pdf" => "ignore", ) if(!%known_content_types); my $req = HTTP::Request->new(GET => "$base_name$path"); my $res = $ua->request($req); if(!defined $res) { print STDERR "Failed to load $base_name$path\n"; return; } elsif (!$res->is_success) { print STDERR "Status ".$res->status_line." when connecting to +$base_name$path\n"; return; } my $page_contents = $res->content(); if(!defined $page_contents || $page_contents eq "") { print STDERR "Failed to find content $path\n"; return; } if(defined $res->headers()->content_type()) { my $content = $res->headers()->content_type(); if($content =~ s/;.*$//) { # The content type could be something like # "text/html; charset=iso-8859-1" } if(!defined $known_content_types{$content}) { print STDERR "Unknown content type \"$content\" for $path\ +n"; print STDERR " Ref from ".keys(%{$ref_from{$path}})."\n" if(defined $ref_from{$path +}); $known_content_types{$content} = "ignore" if($content ne " +"); return; } return if($known_content_types{$content} ne "HTML"); } else { print STDERR "Cannot find content type for $path\n"; return; } # Parse HTML with regex, this bit needs rebuilding while($page_contents =~ s/href\s*\=\s*\"([^\"]+)\"/**ref_done**/i) { my $link_to = $1; # Remove the within page address $link_to =~ s/#.*$//; next if(!$link_to); if($link_to =~ m#https?:#i) { # Link to explicitly external site if(!defined $external_pages{$link_to}) { if(!defined $external_report) { print STDERR "External page (from $path) $link_to\ +n"; } else { print $external_report "External page (from $path) + $link_to\n"; } $external_pages{$link_to} = "noted"; } next; } elsif($link_to =~ s#^\./+##) { # Change from link to . to local $link_to = $dir.$link_to; } elsif($link_to =~ m#javascript:#) { # I ain't going in there... } elsif($link_to =~ m#^/#) { # Absolute path within the web site } elsif($link_to =~ m#^(\w[\w\d_\-\/\.\s]+)$#) { # Change from rel to absolute $link_to = $dir.$link_to; } else { print STDERR "Unparsed href (from $path) => \"$link_to\"\n +"; next; } if(!defined $pages{$link_to}) { $pages{$link_to} = "needs_scan"; } } while($page_contents =~ s/href(.{0,30})/**ref_done**/) { my $href_val = $1; # These are the special cases that we have found previously an +d # are not interesting to us next if($href_val =~ m#<#); next if($href_val =~ m#^\"$#); next if($href_val =~ m#^=\&quot;#); next if($href_val =~ m#^_values#); next if($href_val =~ m#^\"\s+type=#); next if($href_val =~ m#[34]_p#); print STDERR "Cannot parse out (from $path) \"href$1\"\n"; } } $num_pages++; }

    Of course that code is chopped out of a much larger script and not tested, but I think it should give you all the bits you need (well except for extracting href values with a proper parser rather than using regex). Hope it helps.

Re: Detect Broken links
by CountZero (Bishop) on Oct 15, 2009 at 09:56 UTC
    Using LWP::Simple and HTML::SimpleLinkExtor it doesn't have to be more complicated than:
    use strict; use warnings; use LWP::Simple; use HTML::SimpleLinkExtor; my $extor = HTML::SimpleLinkExtor->new('http://www.perlmonks.org/'); $extor->parse_url('http://www.perlmonks.org'); print "Checking $_: ", ( head($_) ? 'Good link' : 'Bad link' ), "\n" for $extor->links
    Do read the docs for HTML::SimpleLinkExtor as it has a lot more functionality, for instance what kind of links you want to extract.

    CountZero

    A program should be light and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little or too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity." - The Tao of Programming, 4.1 - Geoffrey James

      Hi,
      Using HTML::SimpleLinkExtor, can i get the http status of the url hit ?

      Thanks,
      Vishy

      A perl Script without 'strict' is like a House without Roof; Both are not Safe;
        HTML::SimpleLinkExtor only gives you a list of the links in the webpage. To check if you can connect with the resource pointed to by the link I used the head function from LWP::Simple. In scalar context it returns TRUE if successful.

        If you need more detailed information you have to use LWP::UserAgent:

        use strict; use warnings; use LWP::UserAgent; use HTML::SimpleLinkExtor; my $agent = LWP::UserAgent->new; my $extor = HTML::SimpleLinkExtor->new('http://www.perlmonks.org/'); $extor->parse_url('http://www.perlmonks.org'); print "Checking $_: ", $agent->head($_)->code, "\n" for $extor->links
        This will give you the HTTP status code. If you replace ->code by ->message, you get a human readable message instead of the three digit code.

        CountZero

        A program should be light and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little or too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity." - The Tao of Programming, 4.1 - Geoffrey James

Re: Detect Broken links
by merlyn (Sage) on Oct 15, 2009 at 14:53 UTC

Log In?
Username:
Password:

What's my password?
Create A New User
Node Status?
node history
Node Type: perlquestion [id://801302]
Approved by Corion
Front-paged by tye
help
Chatterbox?
and the web crawler heard nothing...

How do I use this? | Other CB clients
Other Users?
Others lurking in the Monastery: (6)
As of 2014-09-22 21:23 GMT
Sections?
Information?
Find Nodes?
Leftovers?
    Voting Booth?

    How do you remember the number of days in each month?











    Results (202 votes), past polls