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MIME::Head(3pm)       User Contributed Perl Documentation      MIME::Head(3pm)

       MIME::Head - MIME message header (a subclass of Mail::Header)

       Before reading further, you should see MIME::Tools to make sure that
       you understand where this module fits into the grand scheme of things.
       Go on, do it now.  I'll wait.

       Ready?  Ok...

           ### Create a new, empty header, and populate it manually:
           $head = MIME::Head->new;
           $head->replace('content-type', 'text/plain; charset=US-ASCII');
           $head->replace('content-length', $len);

           ### Parse a new header from a filehandle:
           $head = MIME::Head->read(\*STDIN);

           ### Parse a new header from a file, or a readable pipe:
           $testhead = MIME::Head->from_file("/tmp/test.hdr");
           $a_b_head = MIME::Head->from_file("cat a.hdr b.hdr |");

           ### Output to filehandle:

           ### Output as string:
           print STDOUT $head->as_string;
           print STDOUT $head->stringify;

   Getting field contents
           ### Is this a reply?
           $is_reply = 1 if ($head->get('Subject') =~ /^Re: /);

           ### Get receipt information:
           print "Last received from: ", $head->get('Received', 0);
           @all_received = $head->get('Received');

           ### Print the subject, or the empty string if none:
           print "Subject: ", $head->get('Subject',0);

           ### Too many hops?  Count 'em and see!
           if ($head->count('Received') > 5) { ...

           ### Test whether a given field exists
           warn "missing subject!" if (! $head->count('subject'));

   Setting field contents
           ### Declare this to be an HTML header:
           $head->replace('Content-type', 'text/html');

   Manipulating field contents
           ### Get rid of internal newlines in fields:

           ### Decode any Q- or B-encoded-text in fields (DEPRECATED):

   Getting high-level MIME information
           ### Get/set a given MIME attribute:
           unless ($charset = $head->mime_attr('content-type.charset')) {
               $head->mime_attr("content-type.charset" => "US-ASCII");

           ### The content type (e.g., "text/html"):
           $mime_type     = $head->mime_type;

           ### The content transfer encoding (e.g., "quoted-printable"):
           $mime_encoding = $head->mime_encoding;

           ### The recommended name when extracted:
           $file_name     = $head->recommended_filename;

           ### The boundary text, for multipart messages:
           $boundary      = $head->multipart_boundary;

       A class for parsing in and manipulating RFC-822 message headers, with
       some methods geared towards standard (and not so standard) MIME fields
       as specified in the various Multipurpose Internet Mail Extensions RFCs
       (starting with RFC 2045)

   Creation, input, and output
       new [ARG],[OPTIONS]
           Class method, inherited.  Creates a new header object.  Arguments
           are the same as those in the superclass.

       from_file EXPR,OPTIONS
           Class or instance method.  For convenience, you can use this to
           parse a header object in from EXPR, which may actually be any
           expression that can be sent to open() so as to return a readable
           filehandle.  The "file" will be opened, read, and then closed:

               ### Create a new header by parsing in a file:
               my $head = MIME::Head->from_file("/tmp/test.hdr");

           Since this method can function as either a class constructor or an
           instance initializer, the above is exactly equivalent to:

               ### Create a new header by parsing in a file:
               my $head = MIME::Head->new->from_file("/tmp/test.hdr");

           On success, the object will be returned; on failure, the undefined

           The OPTIONS are the same as in new(), and are passed into new() if
           this is invoked as a class method.

           Note: This is really just a convenience front-end onto "read()",
           provided mostly for backwards-compatibility with MIME-parser 1.0.

       read FILEHANDLE
           Instance (or class) method.  This initializes a header object by
           reading it in from a FILEHANDLE, until the terminating blank line
           is encountered.  A syntax error or end-of-stream will also halt

           Supply this routine with a reference to a filehandle glob; e.g.,

               ### Create a new header by parsing in STDIN:

           On success, the self object will be returned; on failure, a false

           Note: in the MIME world, it is perfectly legal for a header to be
           empty, consisting of nothing but the terminating blank line.  Thus,
           we can't just use the formula that "no tags equals error".

           Warning: as of the time of this writing, Mail::Header::read did not
           flag either syntax errors or unexpected end-of-file conditions (an
           EOF before the terminating blank line).  MIME::ParserBase takes
           this into account.

   Getting/setting fields
       The following are methods related to retrieving and modifying the
       header fields.  Some are inherited from Mail::Header, but I've kept the
       documentation around for convenience.

       add TAG,TEXT,[INDEX]
           Instance method, inherited.  Add a new occurrence of the field
           named TAG, given by TEXT:

               ### Add the trace information:
                          'from by with smtp');

           Normally, the new occurrence will be appended to the existing
           occurrences.  However, if the optional INDEX argument is 0, then
           the new occurrence will be prepended.  If you want to be explicit
           about appending, specify an INDEX of -1.

           Warning: this method always adds new occurrences; it doesn't
           overwrite any existing occurrences... so if you just want to change
           the value of a field (creating it if necessary), then you probably
           don't want to use this method: consider using "replace()" instead.

       count TAG
           Instance method, inherited.  Returns the number of occurrences of a
           field; in a boolean context, this tells you whether a given field

               ### Was a "Subject:" field given?
               $subject_was_given = $head->count('subject');

           The TAG is treated in a case-insensitive manner.  This method
           returns some false value if the field doesn't exist, and some true
           value if it does.

       decode [FORCE]
           Instance method, DEPRECATED.  Go through all the header fields,
           looking for RFC 1522 / RFC 2047 style "Q" (quoted-printable, sort
           of) or "B" (base64) encoding, and decode them in-place.  Fellow
           Americans, you probably don't know what the hell I'm talking about.
           Europeans, Russians, et al, you probably do.  ":-)".

           This method has been deprecated.  See "decode_headers" in
           MIME::Parser for the full reasons.  If you absolutely must use it
           and don't like the warning, then provide a FORCE:

                     Just shut up and do it.  Not recommended.
                     Provided only for those who need to keep old scripts functioning.

                     Just shut up and do it.  Not recommended.
                     Provided for those who REALLY know what they are doing.

           What this method does.  For an example, let's consider a valid
           email header you might get:

               From: =?US-ASCII?Q?Keith_Moore?= <>
               To: =?ISO-8859-1?Q?Keld_J=F8rn_Simonsen?= <>
               CC: =?ISO-8859-1?Q?Andr=E9_?= Pirard <>
               Subject: =?ISO-8859-1?B?SWYgeW91IGNhbiByZWFkIHRoaXMgeW8=?=

           That basically decodes to (sorry, I can only approximate the Latin
           characters with 7 bit sequences /o and 'e):

               From: Keith Moore <>
               To: Keld J/orn Simonsen <>
               CC: Andr'e  Pirard <>
               Subject: If you can read this you understand the example... cool!

           Note: currently, the decodings are done without regard to the
           character set: thus, the Q-encoding "=F8" is simply translated to
           the octet (hexadecimal "F8"), period.  For piece-by-piece decoding
           of a given field, you want the array context of

           Warning: the CRLF+SPACE separator that splits up long encoded words
           into shorter sequences (see the Subject: example above) gets lost
           when the field is unfolded, and so decoding after unfolding causes
           a spurious space to be left in the field.  THEREFORE: if you're
           going to decode, do so BEFORE unfolding!

           This method returns the self object.

           Thanks to Kent Boortz for providing the idea, and the baseline
           RFC-1522-decoding code.

       delete TAG,[INDEX]
           Instance method, inherited.  Delete all occurrences of the field
           named TAG.

               ### Remove some MIME information:

       get TAG,[INDEX]
           Instance method, inherited.  Get the contents of field TAG.

           If a numeric INDEX is given, returns the occurrence at that index,
           or undef if not present:

               ### Print the first and last 'Received:' entries (explicitly):
               print "First, or most recent: ", $head->get('received', 0);
               print "Last, or least recent: ", $head->get('received',-1);

           If no INDEX is given, but invoked in a scalar context, then INDEX
           simply defaults to 0:

               ### Get the first 'Received:' entry (implicitly):
               my $most_recent = $head->get('received');

           If no INDEX is given, and invoked in an array context, then all
           occurrences of the field are returned:

               ### Get all 'Received:' entries:
               my @all_received = $head->get('received');

           NOTE: The header(s) returned may end with a newline.  If you don't
           want this, then chomp the return value.

       get_all FIELD
           Instance method.  Returns the list of all occurrences of the field,
           or the empty list if the field is not present:

               ### How did it get here?
               @history = $head->get_all('Received');

           Note: I had originally experimented with having "get()" return all
           occurrences when invoked in an array context... but that causes a
           lot of accidents when you get careless and do stuff like this:

               print "\u$field: ", $head->get($field);

           It also made the intuitive behaviour unclear if the INDEX argument
           was given in an array context.  So I opted for an explicit approach
           to asking for all occurrences.

       print [OUTSTREAM]
           Instance method, override.  Print the header out to the given
           OUTSTREAM, or the currently-selected filehandle if none.  The
           OUTSTREAM may be a filehandle, or any object that responds to a
           print() message.

           The override actually lets you print to any object that responds to
           a print() method.  This is vital for outputting MIME entities to

           Also, it defaults to the currently-selected filehandle if none is
           given (not STDOUT!), so please supply a filehandle to prevent

           Instance method.  Return the header as a string.  You can also
           invoke it as "as_string".

       unfold [FIELD]
           Instance method, inherited.  Unfold (remove newlines in) the text
           of all occurrences of the given FIELD.  If the FIELD is omitted,
           all fields are unfolded.  Returns the "self" object.

   MIME-specific methods
       All of the following methods extract information from the following


       Be aware that they do not just return the raw contents of those fields,
       and in some cases they will fill in sensible (I hope) default values.
       Use "get()" or "mime_attr()" if you need to grab and process the raw
       field text.

       Note: some of these methods are provided both as a convenience and for
       backwards-compatibility only, while others (like
       recommended_filename()) really do have to be in MIME::Head to work
       properly, since they look for their value in more than one field.
       However, if you know that a value is restricted to a single field, you
       should really use the Mail::Field interface to get it.

       mime_attr ATTR,[VALUE]
           A quick-and-easy interface to set/get the attributes in structured
           MIME fields:

               $head->mime_attr("content-type"         => "text/html");
               $head->mime_attr("content-type.charset" => "US-ASCII");
               $head->mime_attr(""    => "homepage.html");

           This would cause the final output to look something like this:

               Content-type: text/html; charset=US-ASCII; name="homepage.html"

           Note that the special empty sub-field tag indicates the anonymous
           first sub-field.

           Giving VALUE as undefined will cause the contents of the named
           subfield to be deleted:

               $head->mime_attr("content-type.charset" => undef);

           Supplying no VALUE argument just returns the attribute's value, or
           undefined if it isn't there:

               $type = $head->mime_attr("content-type");      ### text/html
               $name = $head->mime_attr(""); ### homepage.html

           In all cases, the new/current value is returned.

           Instance method.  Try real hard to determine the content transfer
           encoding (e.g., "base64", "binary"), which is returned in all-

           If no encoding could be found, the default of "7bit" is returned I
           quote from RFC 2045 section 6.1:

               This is the default value -- that is, "Content-Transfer-Encoding: 7BIT"
               is assumed if the Content-Transfer-Encoding header field is not present.

           I do one other form of fixup: "7_bit", "7-bit", and "7 bit" are
           corrected to "7bit"; likewise for "8bit".

       mime_type [DEFAULT]
           Instance method.  Try "real hard" to determine the content type
           (e.g., "text/plain", "image/gif", "x-weird-type", which is returned
           in all-lowercase.  "Real hard" means that if no content type could
           be found, the default (usually "text/plain") is returned.  From RFC
           2045 section 5.2:

              Default RFC 822 messages without a MIME Content-Type header are
              taken by this protocol to be plain text in the US-ASCII character
              set, which can be explicitly specified as:

                 Content-type: text/plain; charset=us-ascii

              This default is assumed if no Content-Type header field is specified.

           Unless this is a part of a "multipart/digest", in which case
           "message/rfc822" is the default.  Note that you can also set the
           default, but you shouldn't: normally only the MIME parser uses this

           Instance method.  If this is a header for a multipart message,
           return the "encapsulation boundary" used to separate the parts.
           The boundary is returned exactly as given in the "Content-type:"
           field; that is, the leading double-hyphen ("--") is not prepended.

           Well, almost exactly... this passage from RFC 2046 dictates that we
           remove any trailing spaces:

              If a boundary appears to end with white space, the white space
              must be presumed to have been added by a gateway, and must be deleted.

           Returns undef (not the empty string) if either the message is not
           multipart or if there is no specified boundary.

           Instance method.  Return the recommended external filename.  This
           is used when extracting the data from the MIME stream.  The
           filename is always returned as a string in Perl's internal format
           (the UTF8 flag may be on!)

           Returns undef if no filename could be suggested.

       Why have separate objects for the entity, head, and body?
           See the documentation for the MIME-tools distribution for the
           rationale behind this decision.

       Why assume that MIME headers are email headers?
           I quote from Achim Bohnet, who gave feedback on v.1.9 (I think he's
           using the word "header" where I would use "field"; e.g., to refer
           to "Subject:", "Content-type:", etc.):

               There is also IMHO no requirement [for] MIME::Heads to look
               like [email] headers; so to speak, the MIME::Head [simply stores]
               the attributes of a complex object, e.g.:

                   new MIME::Head type => "text/plain",
                                  charset => ...,
                                  disposition => ..., ... ;

           I agree in principle, but (alas and dammit) RFC 2045 says
           otherwise.  RFC 2045 [MIME] headers are a syntactic subset of
           RFC-822 [email] headers.

           In my mind's eye, I see an abstract class, call it MIME::Attrs,
           which does what Achim suggests... so you could say:

                my $attrs = new MIME::Attrs type => "text/plain",
                                            charset => ...,
                                            disposition => ..., ... ;

           We could even make it a superclass of MIME::Head: that way,
           MIME::Head would have to implement its interface, and allow itself
           to be initialized from a MIME::Attrs object.

           However, when you read RFC 2045, you begin to see how much MIME
           information is organized by its presence in particular fields.  I
           imagine that we'd begin to mirror the structure of RFC 2045 fields
           and subfields to such a degree that this might not give us a
           tremendous gain over just having MIME::Head.

       Why all this "occurrence" and "index" jazz?  Isn't every field unique?

           Looking at a typical mail message header, it is sooooooo tempting
           to just store the fields as a hash of strings, one string per hash
           entry.  Unfortunately, there's the little matter of the "Received:"
           field, which (unlike "From:", "To:", etc.) will often have multiple
           occurrences; e.g.:

               Received: from by  with smtp
                   (Linux Smail3.1.28.1 #5) id m0tStZ7-0007X4C;
                    Thu, 21 Dec 95 16:34 CST
               Received: from by
                    (5.65/Ultrix3.0-C) id AA13596;
                    Thu, 21 Dec 95 17:20:38 -0500
               Received: (from eryq@localhost) by
                    (8.6.12/8.6.12) id RAA28069;
                    Thu, 21 Dec 1995 17:27:54 -0500
               Date: Thu, 21 Dec 1995 17:27:54 -0500
               From: Eryq <>
               Message-Id: <>
               Subject: Stuff and things

           The "Received:" field is used for tracing message routes, and
           although it's not generally used for anything other than human
           debugging, I didn't want to inconvenience anyone who actually
           wanted to get at that information.

           I also didn't want to make this a special case; after all, who
           knows what other fields could have multiple occurrences in the
           future?  So, clearly, multiple entries had to somehow be stored
           multiple times... and the different occurrences had to be

       Mail::Header, Mail::Field, MIME::Words, MIME::Tools

       Eryq (, ZeeGee Software Inc (
       David F. Skoll (

       All rights reserved.  This program is free software; you can
       redistribute it and/or modify it under the same terms as Perl itself.

       The more-comprehensive filename extraction is courtesy of Lee E.
       Brotzman, Advanced Data Solutions.

perl v5.18.1                      2013-11-14                   MIME::Head(3pm)

Czas wygenerowania: 0.00056 sek.

Created with the man page lookup class by Andrew Collington.
Based on a C man page viewer by Vadim Pavlov
Unicode soft-hyphen fix (as used by RedHat) by Dan Edwards
Some optimisations by Eli Argon
Caching idea and code contribution by James Richardson

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