path: root/rfc2045/makemime.sgml

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<refentry>
  <info><author><firstname>Sam</firstname><surname>Varshavchik</surname><contrib>Author</contrib></author><productname>Courier Mail Server</productname></info>

  <refmeta>
    <refentrytitle>makemime</refentrytitle>
    <manvolnum>1</manvolnum>
    <refmiscinfo class='manual'>Double Precision, Inc.</refmiscinfo>
  </refmeta>

  <refnamediv>
    <refname>makemime</refname>
    <refpurpose>Create MIME-formatted messages</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <cmdsynopsis sepchar=" ">
      <command moreinfo="none">makemime</command>
      <arg rep="repeat" choice="opt"><replaceable>options</replaceable></arg>
    </cmdsynopsis>

    <cmdsynopsis sepchar=" ">
      <command moreinfo="none">makemime</command>
      <arg choice="opt" rep="norepeat">@<replaceable>filename</replaceable></arg>
    </cmdsynopsis>
  </refsynopsisdiv>

  <refsect1>
    <title>DESCRIPTION</title>

    <para>
<command moreinfo="none">makemime</command> creates MIME-formatted messages of arbitrary
complexity.
<command moreinfo="none">makemime</command> reads one or more individual files,
MIME-encodes them, adds basic MIME headers, and adds any additional headers
specified bye command line options. The result is saved to another file or
standard output. Complex MIME-formatted messages are created by piping together
multiple instances of <command moreinfo="none">makemime</command>.
Advanced options direct <command moreinfo="none">makemime</command> to
<function moreinfo="none">fork</function>() itself, and handle the details of setting up all
the pipelines.</para>

    <para>
In most cases, options for <command moreinfo="none">makemime</command> come directly from the
command line. @<filename moreinfo="none">filename</filename> reads the options from a file.
"<literal moreinfo="none">@&amp;<replaceable>n</replaceable></literal>" reads options from a pipe
on file descriptor #<replaceable>n</replaceable>.
"<literal moreinfo="none">@-</literal>" is a shortcut for
"<literal moreinfo="none">@&amp;0</literal>", which reads options from standard input.</para>

    <para>
When options are read from a file or a pipe, each option must be on a
line by itself. If an option requires an argument, the argument must follow
on the next line.</para>

    <para>
For readability, leading whitespace is deleted when options
are read from a file or a pipe. Empty lines are also ignored, as well as lines
that begin with the '<token>#</token>' character.</para>

    <para>
Options and their arguments may contain characters that are special
characters to the shell, such as '<token>(</token>' and '<token>)</token>'.
These characters must be backslashed when specified on the command line, to
avoid their special meaning to the shell.
These characters MUST NOT be backslashed when options are read
from a file or a pipe. Similarly, the contents of most headers nearly always
include spaces.  Therefore they must be quoted when specified on the command
line.  Header contents MUST NOT be quoted when options come from a file or a
pipe.</para>

    <para><command moreinfo="none">makemime</command> reads the content to be formatted
as a MIME message from some other file.
The files can also be a pipe. It is possible to supply both the
options and a file from the same pipe, by terminating the options list with
a line containing the single character "-". The remainder of the pipe will be
available to be used as an input file (which must be explicitly specified
by one of the options). Of course, only one input file can come from a single
pipe.</para>

    <refsect2>
<title>MIME overview</title>

      <para>
A MIME-formatted message contains one or several MIME sections. MIME headers
specify how multiple MIME sections are to be interpreted as a whole (whether
they are attached together; whether they are alternative representations of
the same content; or something even more esoteric). This manual page gives a
very brief, terse, overview of basic MIME concepts. The description is biased
towards describing the functionality of the <command moreinfo="none">makemime</command>
utility.
See
<ulink url="http://www.rfc-editor.org/rfc/rfc2045.txt">RFC 2045</ulink>,
<ulink url="http://www.rfc-editor.org/rfc/rfc2046.txt">RFC 2046</ulink>,
<ulink url="http://www.rfc-editor.org/rfc/rfc2047.txt">RFC 2047</ulink>,
<ulink url="http://www.rfc-editor.org/rfc/rfc2048.txt">RFC 2048</ulink>, and
<ulink url="http://www.rfc-editor.org/rfc/rfc2048.txt">RFC 2049</ulink>
for a formal definition of MIME-formatted messages.</para>

      <para>
Each file in a MIME message is encoded as a single MIME section. A MIME
section consists of at least one header line,
"<literal moreinfo="none">Content-Type:</literal>".
The "<literal moreinfo="none">Content-Type:</literal>" header gives the type of the data 
ontained in the file. Other header lines may also be present.
Their relative order does not matter. MIME
headers are followed by a blank line, then the contents of the file, encoded
appropriately.
All MIME sections generated by <command moreinfo="none">makemime</command> will always
contain another header,
"<literal moreinfo="none">Content-Transfer-Encoding:</literal>". This header gives the
encoding method used for the file; it is an optional header, but
<command moreinfo="none">makemime</command> always creates it.</para>

      <para>
The MIME encoding method defaults to
"<literal moreinfo="none">7bit</literal>" if this header is absent.
<literal moreinfo="none">7bit</literal>
encoding is only suitable for plain text messages in the US-ASCII character
set.
The "<literal moreinfo="none">8bit</literal>" encoding method is used by plain text messages
in other character sets that use octets with the high bit set. An
alternative to 8bit encoding is
"<literal moreinfo="none">quoted-printable</literal>". The "<literal moreinfo="none">base64</literal>" encoding
method is used for files containing binary data (anything other than plain
text).</para>

      <para>
MIME sections that contain text messages have their
"<literal moreinfo="none">Content-Type:</literal>" header
set to "<literal moreinfo="none">text/plain</literal>";
or "<literal moreinfo="none">text/html</literal>" for HTML messages.
There are also several
other, rare, content types that can be used. MIME sections that contain other
kinds of data will use some other, appropriate
"<literal moreinfo="none">Content-Type:</literal>" header, such as
"<literal moreinfo="none">image/gif</literal>", or "<literal moreinfo="none">audio/x-wav</literal>".</para>

      <para>
MIME sections that contain textual content may also use the
<literal moreinfo="none">base64</literal> encoding
method, they are not required to use <literal moreinfo="none">7bit</literal>,
<literal moreinfo="none">8bit</literal>, or <literal moreinfo="none">quoted-printable</literal>.
"<literal moreinfo="none">text/pdf</literal>" sections, that contain PDF files,
typically contain binary data
and must use the <literal moreinfo="none">base64</literal> encoding.
Consequently, MIME sections that typically
contain binary data, such as
<literal moreinfo="none">image/gif</literal> and <literal moreinfo="none">audio/x-wav</literal>,
are free to use
encodings other than <literal moreinfo="none">base64</literal>, as long as all the data can
be represented by
printable characters (but, in practice, that never happens).</para>

      <para>
MIME sections may also contain other, optional, headers such as
"<literal moreinfo="none">Content-Disposition:</literal>",
"<literal moreinfo="none">Content-ID:</literal>", and "<literal moreinfo="none">Content-Name:</literal>".
Consult the
appropriate RFCs for the specific usage of these headers. These headers can be
added by <command moreinfo="none">makemime</command> by using the
<option>-a</option> option, as described below. These
headers play no part in creating the overall structure of a MIME-encoded
message, and <command moreinfo="none">makemime</command> does not care much about these
headers. It simply
includes them, and their content, upon request.</para>

      <para>
Multiple files are formatted as a single message MIME message in two steps:
first, by creating a MIME section for each file;
and then creating a single MIME section that contains other MIME sections.
A "<literal moreinfo="none">multipart/mixed</literal>" MIME section contains a
collection of MIME sections that represent different objects, attached
together.
A "<literal moreinfo="none">multipart/alternative</literal>" MIME section contains a
collection of MIME
sections which are alternative representations of the same object, such as an
HTML and a plain text version of the same message. Other "multipart" MIME
sections also exist, and their usage is defined by their respective
RFCs.</para>
    </refsect2>

    <refsect2>
      <title>Creating a single MIME section</title>

      <cmdsynopsis sepchar=" ">
	<command moreinfo="none">makemime</command>
	<arg choice="req" rep="norepeat">-c "<replaceable>type</replaceable>"</arg>
	<arg choice="opt" rep="norepeat">-e "<replaceable>encoding</replaceable>"</arg>
	<arg choice="opt" rep="norepeat">-o <replaceable>outputfile</replaceable></arg>
	<arg choice="opt" rep="norepeat">-C "<replaceable>charset</replaceable>"</arg>
	<arg choice="opt" rep="norepeat">-N "<replaceable>name"</replaceable></arg>
	<arg rep="repeat" choice="opt">-a "<replaceable>header: value"</replaceable></arg>
	<arg choice="req" rep="norepeat"><replaceable>filename</replaceable></arg>
      </cmdsynopsis>

      <para>
The <option>-c</option> option reads <filename moreinfo="none">filename</filename>,
encodes it appropriately, adds the
"<literal moreinfo="none">Content-Type: <replaceable>type</replaceable></literal>" and
"<literal moreinfo="none">Content-Transfer-Encoding:</literal>" MIME headers, then writes the
result to standard output. <literal moreinfo="none">type</literal> can be any valid MIME type,
except for <literal moreinfo="none">multipart</literal>.
Setting <filename moreinfo="none">filename</filename> to "<literal moreinfo="none">-</literal>"
reads from standard input.
Setting <filename moreinfo="none">filename</filename> to "&amp;<replaceable>n</replaceable>"
reads from file descriptor #<replaceable>n</replaceable>.</para>

      <para>
The <option>-C</option> option sets the MIME <literal moreinfo="none">charset</literal>
attribute for <literal moreinfo="none">text/plain</literal> content. The <option>-N</option>
option sets the <literal moreinfo="none">name</literal> attribute for
<literal moreinfo="none">Content-Type:</literal>.</para>

      <para>
<replaceable>encoding</replaceable> argument should be specified. It's more
efficient to do so. <replaceable>encoding</replaceable> must be one of the
following:
<literal moreinfo="none">7bit</literal>, <literal moreinfo="none">8bit</literal>,
<literal moreinfo="none">quoted-printable</literal>, or <literal moreinfo="none">base64</literal>.</para>

      <para>
If <replaceable>encoding</replaceable> is not specified,
<command moreinfo="none">makemime</command>
reads the <filename moreinfo="none">filename</filename> twice - once to figure out the best
encoding method, and the second time to encode <filename moreinfo="none">filename</filename>.
If <filename moreinfo="none">filename</filename> is a pipe <command moreinfo="none">makemime</command>
creates a temporary file, which is not very efficient if
<filename moreinfo="none">filename</filename> is large.
However letting <command moreinfo="none">makemime</command> pick the encoding method
is more convenient if <filename moreinfo="none">filename</filename> is relatively small.</para>

      <para>
Another possibility is to omit <replaceable>encoding</replaceable> and set
<replaceable>type</replaceable> to <literal moreinfo="none">auto</literal>.
This combination sets "<literal moreinfo="none">Content-Type:</literal>" to either
<literal moreinfo="none">text/plain</literal>, or
<literal moreinfo="none">application/octet-stream</literal>, based on the selected
<replaceable>encoding</replaceable>.</para>

      <para>
By default the encoded MIME section is written to standard output.
The <option>-o</option> option writes the MIME section to
<replaceable>outputfile</replaceable>. <replaceable>outputfile</replaceable> may be
"&amp;<replaceable>n</replaceable>",
which writes the MIME section to a pipe on file descriptor
#<replaceable>n</replaceable>.</para>

      <para>
<command moreinfo="none">makemime</command> does not generate any other headers.
Particularly, the
"<literal moreinfo="none">Mime-Version:</literal>" header is required for
MIME-formatted E-mail messages. Additional headers are specified by the
<option>-a</option> option, which may be used
multiple times to insert multiple headers.
<command moreinfo="none">makemime</command> doesn't do anything
with them except to insert the headers into the generated MIME section.</para>

      <para>Note that
"<literal moreinfo="none">Mime-Version:</literal>" is only required for the top level
MIME section.
This header is not required for individual MIME sections that are later
combined into a multipart MIME collection.</para>

      <note>
	<para>
The <option>-c</option> option must occur listed first, the remaining
options must follow the <option>-c</option> option.</para>
      </note>
    </refsect2>

    <refsect2>
      <title>Creating a multipart MIME collection</title>

      <cmdsynopsis sepchar=" ">
	<command moreinfo="none">makemime</command>
	<arg choice="req" rep="norepeat">-m "multipart/<replaceable>type</replaceable>"</arg>
	<arg choice="opt" rep="norepeat">-e "<replaceable>encoding</replaceable>"</arg>
	<arg choice="opt" rep="norepeat">-o <replaceable>outputfile</replaceable></arg>
	<arg rep="repeat" choice="opt">-a "<replaceable>header: value"</replaceable></arg>
	<arg choice="req" rep="norepeat"><replaceable>filename</replaceable></arg>
      </cmdsynopsis>

      <para>
The <option>-m</option> option is identical to the <option>-c</option> option,
except for three differences.</para>

      <para>
<replaceable>type</replaceable> must be either
"<literal moreinfo="none">multipart/mixed</literal>",
"<literal moreinfo="none">multipart/alternative</literal>", or
some other MIME multipart content type. Additionally,
"<replaceable>encoding</replaceable>" can only be
"<literal moreinfo="none">7bit</literal>" or "<literal moreinfo="none">8bit</literal>", and will default to "<literal moreinfo="none">8bit</literal>" if not specified. Finally,
<filename moreinfo="none">filename</filename> must be a MIME-formatted section, NOT a regular
file. Usually
<filename moreinfo="none">filename</filename> is created by a previous
invocation of <command moreinfo="none">makemime</command> (it can also be a pipe, like
the <option>-c</option> option), but it can be created via any other
means.</para>

      <para>
The <option>-m</option> option creates an initial multipart MIME collection,
that contains
only one MIME section, taken from <filename moreinfo="none">filename</filename>.
The collection is written to standard output, or the pipe or
to <replaceable>outputfile</replaceable>.</para>
    </refsect2>

    <refsect2>
      <title>Creating a multipart MIME section</title>

      <cmdsynopsis sepchar=" ">
	<command moreinfo="none">makemime</command>
	<arg choice="req" rep="norepeat">-j <replaceable>file1</replaceable>"</arg>
	<arg choice="opt" rep="norepeat">-o <replaceable>outputfile</replaceable></arg>
	<arg choice="req" rep="norepeat"><replaceable>file2</replaceable></arg>
      </cmdsynopsis>

      <para>
This option adds a MIME section to an existing MIME collection.
<replaceable>file1</replaceable> must be a MIME collection that was
previously created by the <option>-m</option> option.
<replaceable>file2</replaceable> must be a MIME section that was previously
created by the <option>-c</option> option.
The <option>-j</option> options adds the MIME section in
<replaceable>file2</replaceable> to the MIME collection in
<replaceable>file1</replaceable>.  The result is written to standard output
or to <replaceable>outputfile</replaceable>.</para>

      <para>

<replaceable>file1</replaceable> and/or <replaceable>file2</replaceable> may
be
"<literal moreinfo="none">@&amp;<replaceable>n</replaceable></literal>" which reads from
file descriptor #<replaceable>n</replaceable>.
The <replaceable>outputfile</replaceable>
may also specify a file descriptor.</para>

      <para><replaceable>file1</replaceable> and
<replaceable>file2</replaceable> should ideally be created by
<command moreinfo="none">makemime</command> as well.
It's also possible to use MIME-formatted files created by other software, but
with some degree of care. <command moreinfo="none">makemime</command> is not intended to be a
MIME parser, but a MIME generator. However some amount of MIME parsing is
necessary to append a MIME section to an existing MIME collection.
<command moreinfo="none">makemime</command>'s parsing is sufficient
for appending a new section to a MIME collection, as long as the
MIME headers in the MIME collections are straightforward. Very convoluted MIME
headers may confuse <command moreinfo="none">makemime</command>, and it may not be able to
handle them.</para>
    </refsect2>

    <refsect2>
<title>Recursive MIME collections</title>

      <para>
MIME collection may contain other MIME collections as well as MIME
sections. The <option>-m</option> and the <option>-j</option> options may use
a multipart MIME collection in place of a MIME section automatically
because a multipart MIME collection is just a special type of a MIME section.
The following example
encodes a text message that can be alternatively represented as HTML or plain
text, with some additional attachments:</para>

      <para>
1. Create a MIME collection that has a
<literal moreinfo="none">text/plain</literal> and a <literal moreinfo="none">text/html</literal> MIME
section.</para>

      <para>
2. Create a MIME collection consisting of the MIME section generated in
step one, plus additional MIME sections containing other attachments.</para>

      <para>For example:</para>
      <blockquote>
	<informalexample>
	  <programlisting format="linespecific">
# Take two files containing the text and the html version of a message, and
# add MIME headers to them.

makemime -c "text/plain; charset=iso-8859-1" -o tmp1.txt msg.txt
makemime -c "text/html; charset=iso-8859-1" -o tmp1.html msg.html

# Combine the result into a multipart/alternative collection

makemime -m "multipart/alternative" -a "Content-Disposition: inline" \
                                    -o tmp.ma1 tmp1.txt
makemime -j tmp.ma1 -o tmp.ma2 tmp1.html

# Add MIME headers to an image attachment.

makemime -c "image/gif" -a "Content-Disposition: attachment" \
                        -o tmp2.gif attachment.gif

# Create the final multipart/mixed collection

makemime -m "multipart/mixed" -a "Mime-Version: 1.0" \
                              -o tmp.mm1 tmp.ma2
makemime -j tmp.mm1 -o output.msg tmp2.gif
</programlisting>
	</informalexample>
      </blockquote>

      <para>
<filename moreinfo="none">output.msg</filename> now contains the complete MIME collection.
Just add the
<literal moreinfo="none">Subject:</literal>, <literal moreinfo="none">From:</literal>, and
<literal moreinfo="none">To:</literal> headers (can also be done by additional
<option>-a</option> options, of
course), and send it on its way.</para>
    </refsect2>

    <refsect2>
      <title>Building complex MIME encodings</title>

      <para>
There are several different ways to build complete MIME encodings from
multiple MIME sections.  One way is to use temporary files to create MIME
sections, then combine them together into a single MIME collection. A slightly
more complicated approach involves setting up pipes between multiple makemime
processes, in order to avoid using temporary files.</para>

      <para>This can be done manually, by hand. It is also possible to have
<command moreinfo="none">makemime</command> do this automatically. <command moreinfo="none">makemime</command>
will set up these pipes and run multiple instances of itself to create a
single MIME collection, with
multiple attachments of complexity limited only by your system's limit on
the maximum number of open files and pipes.</para>

      <para>
Any file that's read by the
<option>-c</option>,
<option>-m</option>,
and
<option>-j</option>
options (
<option>-o</option>
specifies a file to
create, and doesn't count) may be replaced by a single argument containing a
left parenthesis, additional options, then a single argument containing a
right parenthesis.
A single invocation of <command moreinfo="none">makemime</command> can only use one
<option>-c</option>, <option>-m</option>, or <option>-j</option> option.
However, another <option>-c</option>, <option>-m</option>, or
<option>-j</option> option may be specified
inside the left and the right parenthesis, and its output is used in place of
the file it replaced.  In the previous example the third and the fourth
invocation of <command moreinfo="none">makemime</command> can be replaced with the following
command:</para>

      <blockquote>
	<informalexample>
	  <programlisting format="linespecific">
makemime -j \(                                           \
               -m "multipart/alternative"                \
               -a "Content-Disposition: inline" tmp1.txt \
             \) -o tmp.ma2                               \
             tmp1.html
</programlisting>
	</informalexample>
      </blockquote>

      <para>
Note that the parenthesis must be backslashed, to avoid their special
meaning to the shell. An equivalent argument file would have the following
contents:</para>

      <blockquote>
	<informalexample>
	  <programlisting format="linespecific">
-j
   (
      -m
          multipart/alternative
      -a
          Content-Disposition: inline
      tmp1.txt
   )
   -o
      tmp.ma2
 tmp1.html
</programlisting>
	</informalexample>
      </blockquote>

      <para>
These constructs can be arbitrarily nested, and are limited by the amount
of available memory and resources.  The entire sequence in the previous
section is equivalent to the following command:</para>

      <blockquote>
	<informalexample>
	  <programlisting format="linespecific">
makemime -j                                                 \
         \(                                                 \
            -m "multipart/mixed"                            \
            -a "Mime-Version: 1.0"                          \
            \(                                              \
                -j                                          \
                \(                                          \
                   -m "multipart/alternative"               \
                   -a "Content-Disposition: inline"         \
                   \(                                       \
                      -c "text/plain; charset=iso-8859-1"   \
                      msg.txt                               \
                   \)                                       \
                \)                                          \
                \(                                          \
                    -c "text/html; charset=iso-8859-1"      \
                    msg.html                                \
                \)                                          \
            \)                                              \
         \)                                                 \
         -o output.msg                                      \
         \(                                                 \
            -c "image/gif"                                  \
            -a "Content-Disposition: attachment"            \
            attachment.gif                                  \
         \)
</programlisting>
	</informalexample>
      </blockquote>

      <para>
An equivalent argument file would be:</para>

      <blockquote>
	<informalexample>
	  <programlisting format="linespecific">
-j
(
   -m
       multipart/mixed
   -a
       Mime-Version: 1.0
   (
       -j
       (
           -m
               multipart/alternative
           -a
               Content-Disposition: inline
           (
               -c
                   text/plain; charset=iso-8859-1
               msg.txt
           )
       )
       (
           -c
               text/html; charset=iso-8859-1
           msg.html
       )
   )
)
-o
   output.msg
(
   -c
       image/gif
   -a
       Content-Disposition: attachment
   attachment.gif
)
</programlisting>
	</informalexample>
      </blockquote>
    </refsect2>
  </refsect1>

  <refsect1>
    <title>SEE ALSO</title>

    <para>
<ulink url="maildrop.html"><citerefentry><refentrytitle>maildrop</refentrytitle><manvolnum>1</manvolnum></citerefentry></ulink>,
<ulink url="maildropfilter.html"><citerefentry><refentrytitle>maildropfilter</refentrytitle><manvolnum>5</manvolnum></citerefentry></ulink>,
<ulink url="reformail.html"><citerefentry><refentrytitle>reformail</refentrytitle><manvolnum>1</manvolnum></citerefentry></ulink>,
<ulink url="reformime.html"><citerefentry><refentrytitle>reformime</refentrytitle><manvolnum>1</manvolnum></citerefentry></ulink>,
<citerefentry><refentrytitle>egrep</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>grep</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<ulink url="courier.html"><citerefentry><refentrytitle>courier</refentrytitle><manvolnum>8</manvolnum></citerefentry></ulink>,
<citerefentry><refentrytitle>sendmail</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<ulink url="http://www.rfc-editor.org/rfc/rfc2045.txt">RFC 2045</ulink>,
<ulink url="http://www.rfc-editor.org/rfc/rfc2046.txt">RFC 2046</ulink>,
<ulink url="http://www.rfc-editor.org/rfc/rfc2047.txt">RFC 2047</ulink>,
<ulink url="http://www.rfc-editor.org/rfc/rfc2048.txt">RFC 2048</ulink>,
<ulink url="http://www.rfc-editor.org/rfc/rfc2048.txt">RFC 2049</ulink>.</para>
  </refsect1>
</refentry>