Mailcap files, defined in [RFC 1524][rfc1524], allow you to tell you
mail clients, web browsers, and other programs how you want to view
and edit various MIME types.  Since interaction with your mailcap
files often occurs deep within the bowels of your program, I've
written up a very simple [[Python]] script to test your mailcap
entries: [[mailcap-test.py]].  Enjoy!

Related utilities include [xdg-open][], [mimeopen][], and
[sensible-utils][].

Quoting
-------

Quoting in mailcap files is a tricky issue.  From the [Mutt][] man
page:

> Secure use of mailcap
>
> The interpretion of shell meta-characters embedded in MIME
> parameters can lead to security problems in general. Mutt tries to
> quote parameters in expansion of `%s` syntaxes properly, and avoids
> risky characters by substituting them, see the `mailcap_sanitize`
> variable.
>
> Although mutt's procedures to invoke programs with mailcap seem to
> be safe, there are other applications parsing mailcap, maybe taking
> less care of it. Therefore you should pay attention to the following
> rules:
>
> *Keep the %-expandos away from shell quoting.* Don't quote them with
> single or double quotes. Mutt does this for you, the right way, as
> should any other program which interprets mailcap. Don't put them
> into backtick expansions. Be highly careful with eval statements,
> and avoid them if possible at all. Trying to fix broken behaviour
> with quotes introduces new leaks - there is no alternative to
> correct quoting in the first place.
>
> If you have to use the %-expandos' values in context where you need
> quoting or backtick expansions, put that value into a shell variable
> and reference the shell variable where necessary, as in the
> following example (using $charset inside the backtick expansion is
> safe, since it is not itself subject to any further expansion):
>
>     text/test-mailcap-bug; cat %s; copiousoutput; test=charset=%{charset} \
>         && test "`echo $charset | tr '[A-Z]' '[a-z]'`" != iso-8859-1

[rfc1524]: http://tools.ietf.org/html/rfc1524
[xdg-open]: http://portland.freedesktop.org/xdg-utils-1.0/xdg-open.html
[mimeopen]: http://search.cpan.org/dist/File-MimeInfo/mimeopen
[sensible-utils]: http://packages.debian.org/sid/sensible-utils
[Mutt]: http://www.mutt.org/doc/manual/manual-5.html

[[!tag tags/code]]
[[!tag tags/linux]]
[[!tag tags/programming]]
[[!tag tags/python]]