How to access HTTP headers from a given url?

Question

I am looking for a way to get http headers from a given url. I tried the below code but it is not working:

#!/usr/bin/perl

#use warnings;
#use strict;
use LWP::UserAgent;

my $ua  = LWP::UserAgent->new;
my $res = $ua->get("http://cpan.org");
print $res->header('Content-Length');

The above code prints nothing. So, where am I going wrong here or is there any better way to access headers.

@Kenosis: /facepalm was not connected to the internet while using this script. Anyways how can one extract the user-agent field. I tried $res->header('agent') but it didn't worked or I have to explicitly set User-Agent and than retrieve it. — RanRag
– RanRag, Commented Sep 9, 2012 at 21:36
There's no such thing as a Agent header in an HTTP response. — ikegami
– ikegami, Commented Sep 9, 2012 at 21:43
In case the following may be helpful: How to set User-Agent with LWP? — Kenosis
– Kenosis, Commented Sep 9, 2012 at 21:52

brian d foy · Accepted Answer · 2012-09-09 22:23:02Z

3

You should check the result of the request before you assume that you can use it as if it worked:

use v5.10;

use LWP::UserAgent;

my $ua  = LWP::UserAgent->new;
my $res = $ua->get("http://444.cpan.org");

if( $res->is_success ) {
    say "Content length is ", $res->header('Content-Length');
    }
else {
    say "Error! ", $res->code;
    }

Remember that a Content-Length header does not mean that you had a successful request. An error response might still contain a message body, which would have a length.

answered Sep 9, 2012 at 22:23

brian d foy

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BSen · Accepted Answer · 2012-09-09 21:47:21Z

1

use LWP::UserAgent;

my $ua  = LWP::UserAgent->new;
my $res = $ua->get("http://cpan.org");
print $res->headers->as_string;

answered Sep 9, 2012 at 21:47

BSen

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