MHBUILD(1)MHBUILD(1)NAMEmhbuild - translate MIME composition draft
SYNOPSISmhbuild file [-auto | -noauto] [-list | -nolist] [-realsize | -noreal‐
size] [-headers | -noheaders] [-directives | -nodirectives]
[-rfc934mode | -norfc934mode] [-contentid | -nocontentid] [-ver‐
bose | -noverbose] [-disposition | -nodisposition] [-check |
-nocheck] [-headerencoding encoding-algorithm | -autoheaderencod‐
ing] [-maxunencoded line-length] [-dist] [-version] [-help]
DESCRIPTION
The mhbuild command will translate a MIME composition draft into a
valid MIME message.
mhbuild creates multi-media messages as specified in RFC 2045 to RFC
2049. This includes the encoding of message headers as specified by
RFC 2047, and the encoding of MIME parameters as specified in RFC 2231.
If you specify the name of the composition file as “-”, then mhbuild
will accept the composition draft on the standard input. If the trans‐
lation of this input is successful, mhbuild will output the new MIME
message to the standard output. This argument must be the last argu‐
ment on the command line.
Otherwise if the file argument to mhbuild is the name of a valid compo‐
sition file, and the translation is successful, mhbuild will replace
the original file with the new MIME message. It will rename the origi‐
nal file to start with the “,” character and end with the string
“.orig”, e.g., if you are editing the file “draft”, it will be renamed
to “,draft.orig”. This allows you to easily recover the mhbuild input
file.
Listing the Contents
The -list switch tells mhbuild to list the table of contents associated
with the MIME message that is created.
The -headers switch indicates that a one-line banner should be dis‐
played above the listing. The -realsize switch tells mhbuild to evalu‐
ate the “native” (decoded) format of each content prior to listing.
This provides an accurate count at the expense of a small delay. If
the -verbose switch is present, then the listing will show any “extra”
information that is present in the message, such as comments in the
“Content-Type” header.
If the -disposition switch is present, then the listing will show any
relevant information from the “Content-Disposition” header.
Simplified Attachment Interface
For users who wish to simply attach files to text content, mhbuild will
scan the composition file for “Attach” headers. An “Attach” header
contains a filename that will be appended to the message using normal
MIME encapsulation rules. One filename is allowed per “Attach” header,
but multiple “Attach” headers are allowed ber composition file.
These files will be appended after any other MIME content, including
any content specified by mhbuild directives (see below). See send(1)
for more details.
Translating the Composition File
mhbuild is essentially a filter to aid in the composition of MIME mes‐
sages. mhbuild will convert an mhbuild “composition file” into a valid
MIME message. A mhbuild “composition file” is just a file containing
plain text that is interspersed with various mhbuild directives. When
this file is processed by mhbuild, the various directives will be
expanded to the appropriate content, and will be encoded according to
the MIME standards. The resulting MIME message can then be sent by
electronic mail.
The formal syntax for a mhbuild composition file is defined at the end
of this document, but the ideas behind this format are not complex.
Basically, the body contains one or more contents. A content consists
of either a directive, indicated with a “#” as the first character of a
line; or, plaintext (one or more lines of text). The continuation
character, “\“, may be used to enter a single directive on more than
one line, e.g.,
#image/png \
/home/foobar/junk/picture.png
There are five kinds of directives: “type” directives, which name the
type and subtype of the content; “external-type” directives, which also
name the type and subtype of the content; the “message” directive
(#forw), which is used to forward one or more messages; the “begin”
directive (#begin), which is used to create a multipart content; and
the “on/off/pop” directives (#on, #off, #pop) which control whether any
other directives are honored at all.
The -directives switch allows control over whether mhbuild will honor
any of the “#”-directives. This can also be affected with the #on or
#off directives, and #pop, which restores the state of processing to
that preceding the most recent #on or #off. (The #on, #off, and #pop
directives are always honored, of course.) This allows inclusion of
plain text which looks like mhbuild directives, without causing errors:
#off
#include <stdio.h>
printf("Hello, World!);
#pop
Currently the stack depth for the #on/off/pop directives is 32.
The “type” directive is used to directly specify the type and subtype
of a content. You may only specify discrete types in this manner
(can't specify the types multipart or message with this directive).
You may optionally specify the name of a file containing the contents
in “native” (decoded) format. If this filename starts with the “|”
character, then it represents a command to execute whose output is cap‐
tured accordingly. For example,
#audio/basic |raw2audio -F < /usr/lib/sound/giggle.au
If a filename is not given, mhbuild will look for information in the
user's profile to determine how the different contents should be com‐
posed. This is accomplished by consulting a composition string, and
executing it under /bin/sh, with the standard output set to the con‐
tent. If the -verbose switch is given, mhbuild will echo any commands
that are used to create contents in this way.
The composition string may contain the following escapes:
%a Insert parameters from directive
%f Insert filename containing content
%F %f, and stdout is not re-directed
%s Insert content subtype
%% Insert character %
First, mhbuild will look for an entry of the form:
mhbuild-compose-<type>/<subtype>
to determine the command to use to compose the content. If this isn't
found, mhbuild will look for an entry of the form:
mhbuild-compose-<type>
to determine the composition command. If this isn't found, mhbuild will
complain.
An example entry might be:
mhbuild-compose-audio/basic: record | raw2audio -F
Because commands like these will vary, depending on the display envi‐
ronment used for login, composition strings for different contents
should probably be put in the file specified by the $MHBUILD environ‐
ment variable, instead of directly in your user profile.
The “external-type” directives are used to provide a MIME reference to
a content, rather than enclosing the contents itself (for instance, by
specifying an ftp site). Hence, instead of providing a filename as
with the type directives, external-parameters are supplied. These look
like regular parameters, so they must be separated accordingly. For
example,
#@application/octet-stream; \
type=tar; \
conversions=compress \
[this is the nmh distribution] \
{attachment; filename="nmh.tar.gz"} \
name="nmh.tar.gz"; \
directory="/pub/nmh"; \
site="ftp.math.gatech.edu"; \
access-type=anon-ftp; \
mode="image"
You must give a description string to separate the content parameters
from the external-parameters (although this string may be empty). This
description string is specified by enclosing it within “[]”. A dispo‐
sition string, to appear in a “Content-Disposition” header, may appear
in the optional “{}”.
These parameters are of the form:
access-type= usually anon-ftp, mail-server, or url
name= filename
permission= read-only or read-write
site= hostname
directory= directoryname (optional)
mode= usually ascii or image (optional)
size= number of octets
server= mailbox
subject= subject to send
body= command to send for retrieval
url= URL of content
A mimimum “external-type” directive for the url access-type would be as
follows:
#@application/octet-stream [] access-type=url; \
url="http://download.savannah.gnu.org/releases/nmh/nmh-1.5.tar.gz"
Any long URLs will be wrapped according to RFC 2231 rules.
The “message” directive (#forw) is used to specify a message or group
of messages to include. You may optionally specify the name of the
folder and which messages are to be forwarded. If a folder is not
given, it defaults to the current folder. Similarly, if a message is
not given, it defaults to the current message. Hence, the message
directive is similar to the forw command, except that the former uses
the MIME rules for encapsulation rather than those specified in RFC
934. For example,
#forw +inbox 42 43 99
If you include a single message, it will be included directly as a con‐
tent of type “message/rfc822”. If you include more than one message,
then mhbuild will add a content of type “multipart/digest” and include
each message as a subpart of this content.
If you are using this directive to include more than one message, you
may use the -rfc934mode switch. This switch will indicate that mhbuild
should attempt to utilize the MIME encapsulation rules in such a way
that the “multipart/digest” that is created is (mostly) compatible with
the encapsulation specified in RFC 934. If given, then RFC 934 compli‐
ant user-agents should be able to burst the message on recep‐
tion -- providing that the messages being encapsulated do not contain
encapsulated messages themselves. The drawback of this approach is
that the encapsulations are generated by placing an extra newline at
the end of the body of each message.
The “begin” directive is used to create a multipart content. When
using the “begin” directive, you must specify at least one content
between the begin and end pairs.
#begin
This will be a multipart with only one part.
#end
If you use multiple directives in a composition draft, mhbuild will
automatically encapsulate them inside a multipart content. Therefore
the “begin” directive is only necessary if you wish to use nested mul‐
tiparts, or create a multipart message containing only one part.
For all of these directives, the user may include a brief description
of the content between the “[” character and the “]” character. This
description will be copied into the “Content-Description” header when
the directive is processed.
#forw [important mail from Bob] +bob 1 2 3 4 5
Similarly, a disposition string may optionally be provided between “{”
and “}” characters; it will be copied into the “Content-Disposition”
header when the directive is processed. If a disposition string is
provided that does not contain a filename parameter, and a filename is
provided in the directive, it will be added to the “Content-Disposi‐
tion” header. For example, the following directive:
#text/plain; charset=iso-8859-1 <>{attachment} /tmp/summary.txt
creates these message part headers:
Content-Type: text/plain; charset="iso-8859-1"
Content-Disposition: attachment; filename="summary.txt"
By default, mhbuild will generate a unique “Content-ID:” for each
directive, corresponding to each message part; however, the user may
override this by defining the ID using the “<” and “>” characters. The
-nocontentid switch suppresses creation of all “Content-ID:” headers,
even in the top level of the message.
Normally mhbuild will choose an appropriate Content-Transfer-Encoding
based on the content and the MIME Content-Type. However, you can over‐
ride that in an mhbuild directive by specifying “*” and the encoding.
Acceptable encoding values are “8bit”, “qpρq (for quoted-printable),
and “b64” (for base64 encoding). It should be noted that undesired
results may occur if 8bit or quoted-printable is selected for binary
content, due to the translation between Unix line endings and the line
endings use by the mail transport system.
In addition to the various directives, plaintext can be present.
Plaintext is gathered, until a directive is found or the draft is
exhausted, and this is made to form a text content. If the plaintext
must contain a “#” at the beginning of a line, simply double it, e.g.,
##when sent, this line will start with only one #
If you want to end the plaintext prior to a directive, e.g., to have
two plaintext contents adjacent, simply insert a line containing a sin‐
gle “#” character, e.g.,
this is the first content
#
and this is the second
Finally, if the plaintext starts with a line of the form:
Content-Description: text
then this will be used to describe the plaintext content. You MUST
follow this line with a blank line before starting your text.
By default, plaintext is captured as a text/plain content. You can
override this by starting the plaintext with “#<” followed by a con‐
tent-type specification. For example, e.g.,
#<text/enriched
this content will be tagged as text/enriched
#
and this content will be tagged as text/plain
#
#<application/x-patch [this is a patch]
and this content will be tagged as application/x-patch
Note that if you use the “#<” plaintext-form, then the content-descrip‐
tion must be on the same line which identifies the content type of the
plaintext.
When composing a text content, you may indicate the relevant character
set by adding the “charset” parameter to the directive.
#<text/plain; charset=iso-8859-5
If a text content contains any 8-bit characters (characters with the
high bit set) and the character set is not specified as above, then
mhbuild will assume the character set is of the type given by the stan‐
dard locale(1) environment variables. If these environment variables
are not set, then the character set will be labeled as “x-unknown”.
If a text content contains only 7-bit characters and the character set
is not specified as above, then the character set will be labeled as
“us-ascii”.
By default text content with the high bit set is encoded with a 8bit
Content-Transfer-Encoding. If the text has lines longer than the value
of -maxunencoded (which defaults to 78) then the text is encoded using
the quoted-printable encoding.
The -headerencoding switch will indicate which algorithm to use when
encoding any message headers that contain 8-bit characters. The valid
arguments are base64 for based-64 encoding and quoted for quoted-print‐
able encoding. The -autoheaderencoding switch will instruct mhbuild to
automatically pick the algorithm that results in a shorter encoded
string.
Putting this all together, here is an example of a more complicated
message draft. The following draft will expand into a multipart/mixed
message containing five parts:
To: nobody@nowhere.org
cc:
Subject: Look and listen to me!
--------
The first part will be text/plain
#<text/enriched
The second part will be text/enriched
#
This third part will be text/plain
#audio/basic [silly giggle] \
|raw2audio -F < /usr/lib/sounds/giggle.au
#image/gif [photo of foobar] \
/home/foobar/lib/picture.gif
Integrity Check
If mhbuild is given the -check switch, then it will also associate an
integrity check with each “leaf” content. This will add a Content-MD5
header field to the content, along with the md5 sum of the unencoded
contents, per RFC 1864. This may be used by the receiver of the mes‐
sage to verify that the contents of the message were not changed in
transport.
Transfer Encodings
After mhbuild constructs the new MIME message by parsing directives,
including files, etc., it scans the contents of the message to deter‐
mine which transfer encoding to use. It will check for 8bit data, long
lines, spaces at the end of lines, and clashes with multipart bound‐
aries. It will then choose a transfer encoding appropriate for each
content type.
If an integrity check is being associated with each content by using
the -check switch, then mhbuild will encode each content with a trans‐
fer encoding, even it the content contains only 7-bit data. This is to
increase the likelihood that the content is not changed while in trans‐
port.
Invoking mhbuild
Typically, mhbuild is invoked by the whatnow program. This command
will expect the body of the draft to be formatted as an mhbuild compo‐
sition file. Once you have composed this input file using a command
such as comp, repl, or forw, you invoke mhbuild at the “What now”
prompt with
What now? mime
prior to sending the draft. This will cause whatnow to execute mhbuild
to translate the composition file into MIME format.
Normally it is an error to invoke mhbuild on file that already in MIME
format. The -auto switch will cause mhbuild to exit without error if
the input file already has valid MIME headers. The use of -auto also
enables the -nodirectives switch.
Finally, you should consider adding this line to your profile:
lproc: show
This way, if you decide to list after invoking mime, the command
What now? list
will work as you expect.
The -dist switch is intended to be used by dist. It will cause mhbuild
to not generate any MIME headers in the composition file (such as
“MIME-Version” or “Content-Type”), but it will still encode message
headers according to RFC 2047.
User Environment
Because the environment in which mhbuild operates may vary for a user,
mhbuild will look for the environment variable $MHBUILD. If present,
this specifies the name of an additional user profile which should be
read. Hence, when a user logs in on a particular machine, this envi‐
ronment variable should be set to refer to a file containing defini‐
tions useful for that machine.
Finally, mhbuild will attempt to consult
/usr/local/etc/nmh/mhn.defaults
if it exists.
See "Profile Lookup" in mh-profile(5) for the profile search order, and
for how duplicate entries are treated.
Syntax of Composition Files
The following is the formal syntax of a mhbuild “composition file”.
body ::= 1*(content | EOL)
content ::= directive | plaintext
directive ::= "#" type "/" subtype
0*(";" attribute "=" value)
[ "(" comment ")" ]
[ "<" id ">" ]
[ "[" description "]" ]
[ "{" disposition "}" ]
[ "*8bit" | "*qp" | "*b64" ]
[ filename ]
EOL
| "#@" type "/" subtype
0*(";" attribute "=" value)
[ "(" comment ")" ]
[ "<" id ">" ]
[ "[" description "]" ]
[ "{" disposition "}" ]
[ "*8bit" | "*qp" | "*b64" ]
external-parameters
EOL
| "#forw"
[ "<" id ">" ]
[ "[" description "]" ]
[ "{" disposition "}" ]
[ "+"folder ] [ 0*msg ]
EOL
| "#begin"
[ "<" id ">" ]
[ "[" description "]" ]
[ "{" disposition "}" ]
[ "alternative"
| "parallel"
| something-else ]
EOL
1*body
"#end" EOL
plaintext ::= [ "Content-Description:"
description EOL EOL ]
1*line
[ "#" EOL ]
| "#<" type "/" subtype
0*(";" attribute "=" value)
[ "(" comment ")" ]
[ "[" description "]" ]
[ "{" disposition "}" ]
[ "*8bit" | "*qp" | "*b64" ]
EOL
1*line
[ "#" EOL ]
line ::= "##" text EOL
-- interpreted as "#"text EOL
| text EOL
FILESmhbuild looks for additional user profile files and mhn.defaults in
multiple locations: absolute pathnames are accessed directly, tilde
expansion is done on usernames, and files are searched for in the
user's Mail directory as specified in their profile. If not found
there, the directory “/usr/local/etc/nmh” is checked.
$HOME/.mh_profile The user profile
$MHBUILD Additional profile entries
/usr/local/etc/nmh/mhn.defaults System default MIME profile entries
PROFILE COMPONENTS
Path: To determine the user's nmh directory
Current-Folder: To find the default current folder
mhbuild-compose-<typeTemplate for composing contents
SEE ALSOmhlist(1), mhshow(1), mhstore(1)
Proposed Standard for Message Encapsulation (RFC 934),
The Content-MD5 Header Field (RFC 1864),
Multipurpose Internet Mail Extensions (MIME) Part One: Format of Inter‐
net Message Bodies (RFC 2045),
Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types (RFC
2046),
Multipurpose Internet Mail Extensions (MIME) Part Three: Message Header
Extensions for Non-ASCII Text (RFC 2047),
Multipurpose Internet Mail Extensions (MIME) Part Four: Registration
Procedures (RFC 2048),
Multipurpose Internet Mail Extensions (MIME) Part Five: Conformance
Criteria and Examples (RFC 2049),
Definition of the URL MIME External-Body Access-Type (RFC 2017),
MIME Parameter Value and Encoded Word Extensions: Character Sets, Lan‐
guages, and Continuations (RFC 2231)
DEFAULTS
`-headers'
`-realsize'
`-norfc934mode'
`-contentid'
`-nocheck'
`-noverbose'
`-nodisposition'
`-autoheaderencoding'
`-maxunencoded 78'
nmh-1.6 March 13, 2014 MHBUILD(1)
