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Quite a bit of effort has been made to make Mutt the premier text-mode
MIME MUA. Every effort has been made to provide the functionality that
the discerning MIME user requires, and the conformance to the standards
wherever possible. When configuring Mutt for MIME, there are two extra
types of configuration files which Mutt uses. One is the
There are three areas/menus in Mutt which deal with MIME, they are the pager (while viewing a message), the attachment menu and the compose menu.
Viewing MIME messages in the pager
When you select a message from the index and view it in the pager, Mutt
decodes the message to a text representation. Mutt internally supports
a number of MIME types, including
Mutt will denote attachments with a couple lines describing them. These lines are of the form:
If Mutt cannot deal with a MIME type, it will display a message like:
The default binding for
Finally, you can apply the usual message-related functions (like
resend-message, and the reply
and forward functions) to attachments of type
See the help on the attachment menu for more information.
The compose menu is the menu you see before you send a message. It allows you to edit the recipient list, the subject, and other aspects of your message. It also contains a list of the attachments of your message, including the main body. From this menu, you can print, copy, filter, pipe, edit, compose, review, and rename an attachment or a list of tagged attachments. You can also modifying the attachment information, notably the type, encoding and description.
Attachments appear as follows:
- 1 [text/plain, 7bit, 1K] /tmp/mutt-euler-8082-0 <no description> 2 [applica/x-gunzip, base64, 422K] ~/src/mutt-0.85.tar.gz <no description>
The '-' denotes that Mutt will delete the file after sending (or
postponing, or cancelling) the message. It can be toggled with the
When you add an attachment to your mail message, Mutt searches your
personal mime.types file at
The mime.types file consist of lines containing a MIME type and a space separated list of extensions. For example:
If Mutt can not determine the mime type by the extension of the file you
attach, it will look at the file. If the file is free of binary
information, Mutt will assume that the file is plain text, and mark it
Mutt supports RFC 1524 MIME Configuration, in particular the Unix specific format specified in Appendix A of RFC 1524. This file format is commonly referred to as the mailcap format. Many MIME compliant programs utilize the mailcap format, allowing you to specify handling for all MIME types in one place for all programs. Programs known to use this format include Netscape, XMosaic, lynx and metamail.
In order to handle various MIME types that Mutt can not handle internally, Mutt parses a series of external configuration files to find an external handler. The default search string for these files is a colon delimited list set to
In particular, the metamail distribution will install a mailcap file,
The Basics of the mailcap file
A mailcap file consists of a series of lines which are comments, blank, or definitions.
A comment line consists of a # character followed by anything you want.
A blank line is blank.
A definition line consists of a content type, a view command, and any number of optional fields. Each field of a definition line is divided by a semicolon ';' character.
The content type is specified in the MIME standard type/subtype method.
The view command is a Unix command for viewing the type specified. There are two different types of commands supported. The default is to send the body of the MIME message to the command on stdin. You can change this behaviour by using %s as a parameter to your view command. This will cause Mutt to save the body of the MIME message to a temporary file, and then call the view command with the %s replaced by the name of the temporary file. In both cases, Mutt will turn over the terminal to the view program until the program quits, at which time Mutt will remove the temporary file if it exists.
So, in the simplest form, you can send a text/plain message to the external pager more on stdin:
Or, you could send the message as a file:
Perhaps you would like to use lynx to interactively view a text/html message:
In this case, lynx does not support viewing a file from stdin, so you must use the %s syntax. Note: Some older versions of lynx contain a bug where they will check the mailcap file for a viewer for text/html. They will find the line which calls lynx, and run it. This causes lynx to continuously spawn itself to view the object.
On the other hand, maybe you don't want to use lynx interactively, you just want to have it convert the text/html to text/plain, then you can use:
Perhaps you wish to use lynx to view text/html files, and a pager on all other text formats, then you would use the following:
This is the simplest form of a mailcap file.
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
Advanced mailcap Usage
In addition to the required content-type and view command fields, you can add semi-colon ';' separated fields to set flags and other options. Mutt recognizes the following optional fields:
When searching for an entry in the mailcap file, Mutt will search for
the most useful entry for its purpose. For instance, if you are
attempting to print an
Mutt will skip the
In addition, you can use this with Autoview to denote two commands for viewing an attachment, one to be viewed automatically, the other to be viewed interactively from the attachment menu. In addition, you can then use the test feature to determine which viewer to use interactively depending on your environment.
For Autoview, Mutt will choose the third entry because of the copiousoutput tag. For interactive viewing, Mutt will run the program RunningX to determine if it should use the first entry. If the program returns non-zero, Mutt will use the second entry for interactive viewing.
The various commands defined in the mailcap files are passed to the
Example mailcap files
This mailcap file is fairly simple and standard:
# I'm always running X :) video/*; xanim %s > /dev/null image/*; xv %s > /dev/null # I'm always running netscape (if my computer had more memory, maybe) text/html; netscape -remote 'openURL(%s)'
This mailcap file shows quite a number of examples:
# Use xanim to view all videos Xanim produces a header on startup, # send that to /dev/null so I don't see it video/*; xanim %s > /dev/null # Send html to a running netscape by remote text/html; netscape -remote 'openURL(%s)'; test=RunningNetscape # If I'm not running netscape but I am running X, start netscape on the # object text/html; netscape %s; test=RunningX # Else use lynx to view it as text text/html; lynx %s # This version would convert the text/html to text/plain text/html; lynx -dump %s; copiousoutput # enriched.sh converts text/enriched to text/html and then uses # lynx -dump to convert it to text/plain text/enriched; enriched.sh ; copiousoutput # I use enscript to print text in two columns to a page text/*; more %s; print=enscript -2Gr %s # Netscape adds a flag to tell itself to view jpegs internally image/jpeg;xv %s; x-mozilla-flags=internal # Use xv to view images if I'm running X # In addition, this uses the \ to extend the line and set my editor # for images image/*;xv %s; test=RunningX; \ edit=xpaint %s # Convert images to text using the netpbm tools image/*; (anytopnm %s | pnmscale -xysize 80 46 | ppmtopgm | pgmtopbm | pbmtoascii -1x2 ) 2>&1 ; copiousoutput # Send excel spreadsheets to my NT box application/ms-excel; open.pl %s
In addition to explicitly telling Mutt to view an attachment with the MIME viewer defined in the mailcap file, Mutt has support for automatically viewing MIME attachments while in the pager.
To work, you must define a viewer in the mailcap file which uses the
You then use the
For instance, if you set auto_view to:
Mutt could use the following mailcap entries to automatically view attachments of these types.
Mutt has some heuristics for determining which attachment of a multipart/alternative type to display. First, mutt will check the alternative_order list to determine if one of the available types is preferred. The alternative_order list consists of a number of mimetypes in order, including support for implicit and explicit wildcards, for example:
Next, mutt will check if any of the types have a defined auto_view, and use that. Failing that, Mutt will look for any text type. As a last attempt, mutt will look for any type it knows how to handle.
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