lib::HTTP::HeadUser3Contributed Perl Documenlib::HTTP::Headers(3)NAMEHTTP::Headers - Class encapsulating HTTP Message headers
SYNOPSIS
require HTTP::Headers;
$request = new HTTP::Headers;
DESCRIPTION
The HTTP::Headers class encapsulates HTTP-style message
headers. The headers consist of attribute-value pairs,
which may be repeated, and which are printed in a
particular order.
Instances of this class are usually created as member
variables of the HTTP::Request and HTTP::Response classes,
internal to the library.
METHODS
$h = new HTTP::Headers
Constructs a new HTTP::Headers object. You might pass
some initial attribute-value pairs as parameters to the
constructor. E.g.:
$h = new HTTP::Headers
Date => 'Thu, 03 Feb 1994 00:00:00 GMT',
Content_Type => 'text/html; version=3.2',
Content_Base => 'http://www.sn.no/';
$h->header($field [=> $val],...)
Get or set the value of a header. The header field name
is not case sensitive. To make the life easier for perl
users who wants to avoid quoting before the => operator,
you can use '_' as a synonym for '-' in header names.
The value argument may be a scalar or a reference to a
list of scalars. If the value argument is not defined,
then the header is not modified.
The header() method accepts multiple ($field => $value)
pairs.
The list of previous values for the last $field is
returned. Only the first header value is returned in
scalar context.
$header->header(MIME_Version => '1.0',
User_Agent => 'My-Web-Client/0.01');
$header->header(Accept => "text/html, text/plain, image/*");
$header->header(Accept => [qw(text/html text/plain image/*)]);
@accepts = $header->header('Accept');
24/Aug/1997 perl 5.005, patch 03 1
lib::HTTP::HeadUser3Contributed Perl Documenlib::HTTP::Headers(3)
$h->scan(\&doit)
Apply a subroutine to each header in turn. The callback
routine is called with two parameters; the name of the
field and a single value. If the header has more than one
value, then the routine is called once for each value.
The field name passed to the callback routine has case as
suggested by HTTP Spec, and the headers will be visited in
the recommended "Good Practice" order.
$h->as_string([$endl])
Return the header fields as a formatted MIME header.
Since it internally uses the scan() method to build the
string, the result will use case as suggested by HTTP
Spec, and it will follow recommended "Good Practice" of
ordering the header fieds. Long header values are not
folded.
The optional parameter specifies the line ending sequence
to use. The default is "\n". Embedded "\n" characters in
the header will be substitued with this line ending
sequence.
$h->push_header($field, $val)
Add a new field value of the specified header. The header
field name is not case sensitive. The field need not
already have a value. Previous values for the same field
are retained. The argument may be a scalar or a reference
to a list of scalars.
$header->push_header(Accept => 'image/jpeg');
$h->remove_header($field,...)
This function removes the headers with the specified
names.
$h->clone
Returns a copy of this HTTP::Headers object.
CONVENIENCE METHODS
The most frequently used headers can also be accessed
through the following convenience methods. These methods
can both be used to read and to set the value of a header.
The header value is set if you pass an argument to the
method. The old header value is always returned.
Methods that deal with dates/times always convert their
value to system time (seconds since Jan 1, 1970) and they
also expect this kind of value when the header value is
24/Aug/1997 perl 5.005, patch 03 2
lib::HTTP::HeadUser3Contributed Perl Documenlib::HTTP::Headers(3)
set.
$h->date
This header represents the date and time at which the
message was originated. E.g.:
$h->date(time); # set current date
$h->expires
This header gives the date and time after which the entity
should be considered stale.
$h->if_modified_since
This header is used to make a request conditional. If the
requested resource has not been modified since the time
specified in this field, then the server will return a
"304 Not Modified" response instead of the document
itself.
$h->last_modified
This header indicates the date and time at which the
resource was last modified. E.g.:
# check if document is more than 1 hour old
if ($h->last_modified < time - 60*60) {
...
}
$h->content_type
The Content-Type header field indicates the media type of
the message content. E.g.:
$h->content_type('text/html');
The value returned will be converted to lower case, and
potential parameters will be chopped off and returned as a
separate value if in an array context. This makes it safe
to do the following:
if ($h->content_type eq 'text/html') {
# we enter this place even if the real header value happens to
# be 'TEXT/HTML; version=3.0'
...
}
24/Aug/1997 perl 5.005, patch 03 3
lib::HTTP::HeadUser3Contributed Perl Documenlib::HTTP::Headers(3)
$h->content_encoding
The Content-Encoding header field is used as a modifier to
the media type. When present, its value indicates what
additional encoding mechanism has been applied to the
resource.
$h->content_length
A decimal number indicating the size in bytes of the
message content.
$h->title
The title of the document. In libwww-perl this header
will be initialized automatically from the
<TITLE>...</TITLE> element of HTML documents. This header
is no longer part of the HTTP standard.
$h->user_agent
This header field is used in request messages and contains
information about the user agent originating the request.
E.g.:
$h->user_agent('Mozilla/1.2');
$h->server
The server header field contains information about the
software being used by the originating server program
handling the request.
$h->from
This header should contain an Internet e-mail address for
the human user who controls the requesting user agent.
The address should be machine-usable, as defined by
RFC822. E.g.:
$h->from('Gisle Aas <aas@sn.no>');
$h->referer
Used to specify the address (URI) of the document from
which the requested resouce address was obtained.
$h->www_authenticate
This header must be included as part of a "401
Unauthorized" response. The field value consist of a
challenge that indicates the authentication scheme and
24/Aug/1997 perl 5.005, patch 03 4
lib::HTTP::HeadUser3Contributed Perl Documenlib::HTTP::Headers(3)
parameters applicable to the requested URI.
$h->authorization
A user agent that wishes to authenticate itself with a
server, may do so by including this header.
$h->authorization_basic
This method is used to get or set an authorization header
that use the "Basic Authentication Scheme". In array
context it will return two values; the user name and the
password. In scalar context it will return
"uname:password" as a single string value.
When used to set the header value, it expects two
arguments. E.g.:
$h->authorization_basic($uname, $password);
24/Aug/1997 perl 5.005, patch 03 5