@c This is part of the GNU Mailutils manual.
@c Copyright (C) 2006, 2007, 2008, 2010 Free Software Foundation, Inc.
@c See file mailutils.texi for copying conditions.
@comment *******************************************************************

The primary aim of this implementation is to provide an interface
between Mailutils and Emacs using mh-e module.

To use Mailutils MH with Emacs, add the following line to your
site-start.el or .emacs file:

(load "mailutils-mh")

For the information about the current state of Mailutils MH
implementation please refer to file @file{mh/TODO} in the Mailutils
distribution directory.

[FIXME]

@menu
* Diffs::      Major differences between Mailutils MH and other MH
               implementations.
@end menu

@node Diffs
@subsection Major differences between Mailutils MH and other MH implementations

@enumerate 1
@item All programs use usual GNU long options. The support for MH single-dash
options is provided for backward compatibility;

@item UUCP addresses are not supported;

@item Mailutils supports a set of new format specifications
(@pxref{Format String Diffs});

@item Mailutils provides a set of new profile variables
(@pxref{Profile Variable Diffs});

@item Several programs behave differently (@pxref{Program
Diffs});

@end enumerate

@menu
* Format String Diffs::
* Profile Variable Diffs::
* Program Diffs::
@end menu

@node Format String Diffs
@subsubsection New and Differing MH Format Specifications

@anchor{decode function}
@deftypefn {MH Format} string decode (string @var{str})

Decodes the input string @var{str} as per RFC 2047. Useful in printing
@samp{From:}, @samp{To:} and @samp{Subject:} headers.

Notice that, unlike the similar NMH function, @code{decode} checks the value
of the global profile variable @code{Charset} (@pxref{Charset variable})
to determine the charset to output the result in. If this variable is
not set, @code{decode} returns its argument without any change. If
this variable is set to @code{auto}, @code{decode} tries to determine
the charset name from the setting of @env{LC_ALL} environment
variable. Otherwise, the value of @code{Charset} is taken to be the
name of the character set.
@end deftypefn

@deftypefn {MH Format} string package ()

Returns package name (string @samp{mailutils}).
@end deftypefn

@deftypefn {MH Format} string package_string ()

Returns full package string (e.g. @samp{GNU Mailutils 2.1})
@end deftypefn

@deftypefn {MH Format} string version ()

Returns mailutils version.
@end deftypefn

@deftypefn {MH Format} string unre (string @var{str})

The function removes any leading whitespace and eventual @samp{Re:} prefix
from its argument. Useful for creating subjects in reply messages:

@smallexample
  %<@{subject@}Subject: Re: %(unre@{subject@})\\n%>
@end smallexample
@end deftypefn

@anchor{reply_regex function}
@deftypefn {MH Format} void reply_regex (string @var{r})

Sets the regular expression used to recognize reply messages. The
argument @var{r} should be a POSIX extended regular expression. 
Matching is case insensitive. 

For example, the following invocation

@smallexample
  %(reply_regex ^\(re|aw|ang|odp\)\(\\[[0-9]+\\]\)?:[[:blank:]])
@end smallexample

@noindent
corresponds to English @samp{Re}, Polish @samp{Odp}, Norwegian @samp{Aw} or
German @samp{Ang}, optionally followed by a number in brackets, followed
by colon and any amount of whitespace. Notice proper quoting of the
regex metacharacters.

See also @code{Reply-Regex} (@pxref{Reply-Regex variable}) and
@code{isreply} (@pxref{isreply MH function}) below.

@end deftypefn

@anchor{isreply MH function}
@deftypefn {MH Format} boolean isreply ([string @var{str}])

If @var{str} is not given, the value of @samp{Subject:} header is taken.

The function returns true if its argument matches the ``reply subject''
regular expression. This expression is set via the global profile variable
@code{Reply-Regex} (@pxref{Reply-Regex variable}) or via the format
function @code{reply_regex}. 

This function is useful for creating @samp{Subject:} headers in reply
messages. For example, consider the following construction:

@smallexample
@group
%<@{subject@}%(lit)%<(isreply)%?\
(profile reply-prefix)%(concat)%|%(concat Re:)%>\
%(concat@{subject@})%(printhdr Subject: )\n%>
@end group
@end smallexample

If the @samp{Subject:} header already contained reply prefix, this construct
leaves it unchanged. Otherwise it prepends to it the value of
@code{Reply-Prefix} profile variable, or, if it is unset, the string
@samp{Re:}. 

This expression is used in default @file{replcomps} and
@file{replgroupcomps} files.
@end deftypefn

@deftypefn {MH Format} boolean rcpt (@samp{to} | @samp{cc} | @samp{me} | @samp{all})

This function returns true if the given element is present in the
recipient mask (as modified by @option{--cc} or @option{--nocc} options) and
false otherwise. It is used in default formats for @command{repl} and
@command{comp}, e.g.: 

@smallexample
%(lit)%<(rcpt to)%(formataddr@{to@})%>
@end smallexample

Notice that this means that usual @file{replcomps} file will be ignoring
@option{--cc} and @option{--nocc} options, unless it has been modified
as shown above. 
@end deftypefn

@deftypefn {MH Format} string concat ()

Appends whitespace + arg to string register.
@end deftypefn

@deftypefn {MH Format} string printhdr (string @var{str})

Prints the value of string register, prefixed by @var{str}.
The output is formatted as a RFC 822 header, i.e.
it is split at whitespace characters nearest to the width boundary
and each subsequent segment is prefixed with horizontal tabulation.
@end deftypefn

@deftypefn {MH Format} string in_reply_to ()

Generates the value for @samp{In-reply-to:} header according to RFC
2822. 
@end deftypefn

@deftypefn {MH Format} string references ()

Generates the value for @samp{References:} header according to RFC 2822.
@end deftypefn

@node Profile Variable Diffs
@subsubsection New MH Profile Variables

@anchor{Charset variable}
@deftypevar {MH Variable} string Charset

Controls the character set in which the components decoded via
the @code{decode} (@pxref{decode function}) format function should be
output.
@end deftypevar

@anchor{Reply-Regex variable}
@deftypevar {MH Variable} string Reply-Regex

Keeps the regular expression used to recognize reply messages. The
argument should be a POSIX extended regular expression. Matching
is case insensitive. 

For more information, please see @xref{reply_regex function}.
@end deftypevar

@node Program Diffs
@subsubsection Differences in MH Program Behavior

@table @command
@item burst

The utility is able to burst both RFC 934 digest messages and MIME
multipart messages. It provides two additional command line options:
@option{--recurse} and @option{--length}.

The @option{--recurse} option instructs the utility to recursively
expand the digest.

The @option{--length} option can be used to set the minimal encapsulation
boundary length for RFC 934 digests. Default length is 1,
i.e. encountering one dash immediately following a newline triggers
digest decoding. It is OK for messages that follow RFC 934
specification. However, many user agents do not precisely follow it,
in particular, they often do not escape lines starting with a dash by
@samp{- } sequence. @command{Mailman} is one of such agents. To cope
with such digests you can set encapsulation boundary length to a higher
value. For example, @command{bounce --length=8} has been found to be
sufficient for most Mailman-generated digests.

@item comp

Understands @option{--build} option.

@item fmtdump

This command is not provided. Use @option{fmtcheck} instead.

@item mhl

If the argument to @code{ignores} contains more than one component name
it must be enclosed in double-quotes. Dangling equal sign is an error,
to set a string variable to the empty value assign it an empty string, e.g.:
@code{overflowtext=""} (see the supplied @file{mhl.format} file).

Interactive prompting is not yet implemented.

@item mhn

@itemize @bullet

@item New option
New option @option{--compose} forces @command{mhn} editing mode. This
is also the default mode. This differs from the standard
@command{mhn}, which switches to the editing mode only if no other
options were given and the input file name coincides with the value of
@env{mhdraft} environment variable.  

@item Show mode (@option{--show})
If an appropriate mhn-show-type[/subtype] was not found, GNU @command{mhn}
prints the decoded message content using @code{moreproc}
variable. Standard @command{mhn} in this case used to print @samp{don't
know how to display content} diagnostic. 

The default behaviour is to pipe the content to the standard input
of the mhn-show-type[/subtype] command. This is altered to using a
temporary file if the command contains @code{%f} or @code{%F} escapes.

@item Store mode (@option{--store})
If the @code{Content-Disposition} header contains @samp{filename=},
and @command{mhn} is invoked with @option{--auto} switch, it
transforms the file name into the absolute notation and uses it only
if it lies below the current mhn-storage directory. Standard
@command{mhn} only requires that the file name do not begin with @samp{/}.

Before saving a message part, GNU @command{mhn} checks if the file already
exists. If so, it asks whether the user wishes to rewrite it. This
behaviour is disabled when @option{--quiet} option was given.
@end itemize

@item mhparam

The @option{--all} mode does not display commented out entries.

@item repl

Understands @option{--use} option. Disposition shell provides
@code{use} command. 

@item rmm

@enumerate 1
@item
Different behaviour if one of the messages in the list does not exist:

Mailutils @command{rmm} does not delete any messages. Standard
@command{rmm} in this case deletes all messages preceding the
non-existent one. 

@item
The @code{rmmproc} profile component is not used.
@end enumerate

@item pick

The non-standard command line syntax @option{--@var{field}
@var{string}}), where @var{field} is any string, is deprecated. It is
recognized only if @command{pick} is called from within another
program, so that existing application continue to work. Please use the
following syntax instead:

@smallexample
pick --component @var{field} --pattern @var{string}
@end smallexample

New command line option @option{--cflags} allows to control the type of 
regular expressions used. The option must occur right before
@option{--pattern} or @option{--component} option (or one of its
aliases, like @option{--cc}, @option{--from}, etc.)

The argument to this option is a string of type specifications:

@multitable @columnfractions 0.20 0.80
@item B @tab Use basic regular expressions
@item E @tab Use extended regular expressions
@item I @tab Ignore case
@item C @tab Case sensitive
@end multitable

Default is @samp{EI}.

The flags remain in effect until the next occurrence of @option{--cflags}
option.

Sample usage:

@smallexample
pick --cflag BC --subject '*a string' 
@end smallexample

The date comparison options (@option{--before} and @option{--after}
accept date specifications in a wide variety of formats, e.g.:

@smallexample
pick --after 20030301
pick --after 2003-03-01
pick --after 01-mar-2003
pick --after 2003-mar-01
pick --before '1 year ago'
etc...
@end smallexample

@item refile

@enumerate
@item
Linking messages between folders goes against the logic of Mailutils,
so @command{refile} never makes links even if called with
@option{--link} option. The latter is actually a synonym for @option{--copy},
which preserves the original message.

@item
The @option{--preserve} option is not implemented. It is retained for backward
compatibility only.

@item
Message specs and folder names may be interspersed.
@end enumerate

@item sortm

New option @option{--numfield} specifies numeric comparison for the
given field. 

Any number of @option{--datefield}, @option{--textfield} and
@option{--numfield} options may be given, thus allowing to build sort
criteria of arbitrary complexity. 

The order of @option{--.*field} options sets the ordering priority. This
differs from the behaviour of the standard @command{sortm}, which
always orders datefield-major, textfield-minor.

Apart from sorting the mailfolder the following actions may be
specified:

@table @option
@item --list
List the ordered messages using a format string given by
@option{--form} or @option{--format} option.

@item --dry-run
Do not actually sort messages, rather print what would have been
done. This is useful for debugging purposes.
@end table

@end table