:mod:`mailcap` --- Mailcap file handling

========================================

.. module:: mailcap

   :synopsis: Mailcap file handling.

Mailcap files are used to configure how MIME-aware applications such as mail

readers and Web browsers react to files with different MIME types. (The name

"mailcap" is derived from the phrase "mail capability".)  For example, a mailcap

file might contain a line like ``video/mpeg; xmpeg %s``.  Then, if the user

encounters an email message or Web document with the MIME type

:mimetype:`video/mpeg`, ``%s`` will be replaced by a filename (usually one

belonging to a temporary file) and the :program:`xmpeg` program can be

automatically started to view the file.

The mailcap format is documented in :rfc:`1524`, "A User Agent Configuration

Mechanism For Multimedia Mail Format Information," but is not an Internet

standard.  However, mailcap files are supported on most Unix systems.

.. function:: findmatch(caps, MIMEtype[, key[, filename[, plist]]])

   Return a 2-tuple; the first element is a string containing the command line to

   be executed (which can be passed to :func:`os.system`), and the second element

   is the mailcap entry for a given MIME type.  If no matching MIME type can be

   found, ``(None, None)`` is returned.

   *key* is the name of the field desired, which represents the type of activity to

   be performed; the default value is 'view', since in the  most common case you

   simply want to view the body of the MIME-typed data.  Other possible values

   might be 'compose' and 'edit', if you wanted to create a new body of the given

   MIME type or alter the existing body data.  See :rfc:`1524` for a complete list

   of these fields.

   *filename* is the filename to be substituted for ``%s`` in the command line; the

   default value is ``'/dev/null'`` which is almost certainly not what you want, so

   usually you'll override it by specifying a filename.

   *plist* can be a list containing named parameters; the default value is simply

   an empty list.  Each entry in the list must be a string containing the parameter

   name, an equals sign (``'='``), and the parameter's value.  Mailcap entries can

   contain  named parameters like ``%{foo}``, which will be replaced by the value

   of the parameter named 'foo'.  For example, if the command line ``showpartial

   %{id} %{number} %{total}`` was in a mailcap file, and *plist* was set to

   ``['id=1', 'number=2', 'total=3']``, the resulting command line would be

   ``'showpartial 1 2 3'``.

   In a mailcap file, the "test" field can optionally be specified to test some

   external condition (such as the machine architecture, or the window system in

   use) to determine whether or not the mailcap line applies.  :func:`findmatch`

   will automatically check such conditions and skip the entry if the check fails.

.. function:: getcaps()

   Returns a dictionary mapping MIME types to a list of mailcap file entries. This

   dictionary must be passed to the :func:`findmatch` function.  An entry is stored

   as a list of dictionaries, but it shouldn't be necessary to know the details of

   this representation.

   The information is derived from all of the mailcap files found on the system.

   Settings in the user's mailcap file :file:`$HOME/.mailcap` will override

   settings in the system mailcap files :file:`/etc/mailcap`,

   :file:`/usr/etc/mailcap`, and :file:`/usr/local/etc/mailcap`.

An example usage::

   >>> import mailcap

   >>> d=mailcap.getcaps()

   >>> mailcap.findmatch(d, 'video/mpeg', filename='/tmp/tmp1223')

   ('xmpeg /tmp/tmp1223', {'view': 'xmpeg %s'})