Text::Header(3) RFC 822/2068 header and unheader functions

SYNOPSIS


use Text::Header; # header and unheader exported
# Construct headers similar to CGI.pm and HTTP::Headers
@HEADERS = header(content_type => 'text/html',
author => 'Nathan Wiger',
last_modified => $date,
accept => [qw(text/html text/plain)]);
# The above produces the array:
@HEADERS = ("Content-Type: text/html\n",
"Author: Nathan Wiger\n",
"Last-Modified: Wed Sep 27 13:31:06 PDT 2000\n",
"Accept: text/html, text/plain\n");
# Can also construct SMTP headers to format mail
@mail_headers = header(from => 'Nathan Wiger <[email protected]>',
to => '[email protected]');

print $MAIL @mail_headers, "\nKeep up the great work!\n";
# The above would print this to the $MAIL handle:
From: Nathan Wiger <[email protected]>
To: [email protected]
Keep up the great work!

DESCRIPTION

This module provides two new functions, "header" and "unheader", which provide general-purpose RFC 822 header construction and parsing. They do not provide any intelligent defaults of HTTP-specific methods. They are simply aimed at providing an easy means to address the mechanics of header parsing.

The output style is designed to mimic "CGI.pm" and "HTTP::Headers", so that users familiar with these interfaces will feel at home with these functions. As shown above, the "headers" function automatically does the following: 

   1. uc's the first letter of each tag token and lc's the
      rest, also converting _'s to -'s automatically
   2. Adds a colon separating each tag and its value, and
      exactly one newline after each one
   3. Combines list elements into a comma-delimited
      string

Note that a list is always joined into a comma-delimited string. To insert multiple separate headers, simply call "header" with multiple args: 

   push @out, header(accept => 'text/html',
                     accept => 'text/plain');

This would create multiple ``Accept:'' lines.

Note that unlike "CGI.pm", the "header" function provided here does not provide any intelligent defaults. If called as: 

    @out_headers = header;

It will return an empty list. This allows "header" to be more general pupose, so it can provide SMTP and other headers as well. You can also use it as a generic text formatting tool, hence the reason it's under the "Text::" hierarchy.

The "unheader" function works in exactly the opposite direction from "header", pulling apart headers and returning a list. "unheader": 

   1. lc's the entire tag name, converting -'s to _'s
   2. Separates each tag based on the colon delimiter,
      chomping newlines.
   3. Returns a list of tag/value pairs for easy assignment
      to a hash

So, assuming the @HEADERS array shown up top: 

   %myheaders = unheader(@HEADERS);

The hash %myheaders would have the following values: 

   %myheaders = (
       content_type => 'text/html',
       author => 'Nathan Wiger',
       last_modified => 'Wed Sep 27 13:31:06 PDT 2000',
       accept => 'text/html, text/plain'
   );

Note that all keys are converted to lowercase, and their values have their newlines stripped. However, note that comma-separated fields are not split up on input. This cannot be done reliably because some fields, such as the HTTP "Date:" header, can contain commas even though they are not lists. Inferring this type of structure would require knowledge of content, and these functions are specifically designed to be content-independent.

The "unheader" function will respect line wrapping, as seen in SMTP headers. It will simply join the lines and return the value, so that: 

   %mail = unheader("To: Nathan Wiger <[email protected]>,
                             [email protected]");

Would return: 

   $mail{to} = "Nathan Wiger <[email protected]>, [email protected]"

Notice that multiple spaces between the comma separator have been condensed to a single space. Since the "header" and "unheader" functions are direct inverses, this call: 

   @out = header unheader @in;

Will result in @out being exactly equivalent to @in.

REFERENCES

This is designed as both a Perl 5 module and also a Perl 6 prototype. Please see the Perl 6 proposal at http://dev.perl.org/rfc/333.html

This module is designed to be fully compliant with the internet standards RFC 822 (SMTP Headers) and RFC 2068 (HTTP Headers).

AUTHOR

Copyright (c) 2000 Nathan Wiger <[email protected]>. All Rights Reserved.

This module is free software; you may copy this under the terms of the GNU General Public License, or the Artistic License, copies of which should have accompanied your Perl kit.

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