.TH MHFIXMSG %manext1% "March 18, 2013" "%nmhversion%"
.\"
.\" %nmhwarning%
.\"
.SH NAME
mhfixmsg \- rewrite MIME messages with various transformations
.SH SYNOPSIS
.HP 5
.na
.B mhfixmsg
.RI [ +folder ]
.RI [ msgs ]
.RB [ \-decodetext
8bit/7bit |
.BR \-nodecodetext ]
.RB [ \-textcodeset
.I codeset
.RB "| " \-notextcodeset ]
.RB [ \-reformat " | " \-noreformat ]
.RB [ \-fixboundary " | " \-nofixboundary ]
.RB [ \-fixcte " | " \-nofixcte ]
.RB [ \-file
.IR file ]
.RB [ \-outfile
.IR outfile ]
.RB [ \-rmmproc
.IR program ]
.RB [ \-normmproc ]
.RB [ \-verbose " | " \-noverbose ]
.RB [ \-version ]
.RB [ \-help ]
.ad
.SH DESCRIPTION
.B mhfixmsg
rewrites MIME messages, applying specific transformations such as
decoding of MIME-encoded message parts and repairing invalid MIME
headers.
.PP
MIME messages are specified in RFC\-2045 to RFC\-2049
(see
.IR mhbuild (1)).
The
.B mhlist
command is invaluable for viewing the content structure of MIME
messages.
.B mhfixmsg
passes non-MIME messages through without any transformations.  If no
transformations apply to a MIME message, the original message or file
is not modified or removed.
.PP
The
.B \-decodetext
switch enables a transformation to decode each base64 and
quoted-printable text message part to the selected 8bit or 7bit
encoding.  If the decoded text would not fit the selected encoding as
defined by RFC-2045, the part is not decoded.
.PP
The
.B \-textcodeset
switch specifies that all text/plain parts of the message(s)
should be converted to
.IR codeset .
Codeset conversions require that
.B nmh
be built with
.IR iconv (3).
To convert text parts other than text/plain, an external program can
be used, via the
.B \-reformat
switch.
.PP
The
.B \-reformat
switch enables a transformation for text parts in the message.  For
each text part that is not text/plain and that does not have a
corresponding text/plain in a multipart/alternative part,
.B mhfixmsg
looks for a mhfixmsg-format-text/subtype profile entry that matches
the subtype of the part.  If one is found and can be used to
successfully convert the part to text/plain,
.B mhfixmsg
inserts that text/plain part at the beginning of the containing
multipart/alternative part, if present.  If not, it creates a
multipart/alternative part.
.PP
.B \-reformat
requires a profile entry for each text part subtype to be reformatted.
The mhfixmsg-format-text/subtype profile entries are based on external
conversion programs, and are used the same way that
.B mhshow
uses its mhshow-show-text/subtype entries.  When
.B nmh
is installed, it searches for a conversion program for text/html
content, and if one is found, inserts a mhfixmsg-format-text/html
entry in %etcdir%/mhn.defaults.  An entry of the same name in the
user's profile takes precedence.  The user can add entries for
other text subtypes to their profile.
.PP
The
.B \-fixboundary
switch enables a transformation to repair the boundary portion of the
Content-Type header field of the message to match the boundaries of
the outermost multipart part of the message, if it does not.  That
condition is indicated by a \*(lqbogus multipart content in
message\*(rq error message from
.B mhlist
and other
.B nmh
programs that parse MIME messages.
.PP
The
.B \-fixcte
switch enables a transformation to change the
Content-Transfer-Encoding from an invalid value to 8bit in message
parts with a Content-Type of multipart, as required by RFC 2045,
Section 6.4.  That condition is indicated by a \*(lqmust be encoded in
7bit, 8bit, or binary\*(rq error message from
.B mhlist
and other
.B nmh
programs that parse MIME messages.
.PP
The
.B \-verbose
switch directs
.B mhfixmsg
to output informational message for each transformation applied.
.PP
The
.B \-file
.I file
switch directs
.B mhfixmsg
to use the specified
file as the source message, rather than a message from a folder.
If this file is \*(lq-\*(rq, then
.B mhfixmsg
accepts the source message on the standard input stream.  If
the
.B \-outfile
switch is not enabled when using the standard input stream,
.B mhfixmsg
will not produce a transformed output message.
.PP
.BR mhfixmsg ,
by default, transforms the message in place.  If the
.B \-outfile
switch is enabled, then
.B mhfixmsg
does not modify the input message or file, but instead places its
output in the specified file.  An outfile name of \*(lq-\*(rq
specifies the standard output stream.
.PP
Combined with the
.B \-verbose
switch, the
.B \-outfile
switch can be used to show what transformations
.B mhfixmsg
would apply without actually applying them, e.g.,
.PP
.RS 5
mhfixmsg -outfile /dev/null -verbose
.RE
.PP
As always, this usage obeys any
.B mhfixmsg
switches in the user's profile.
.PP
.B \-outfile
can be combined with
.B rcvstore
to add a single transformed message to a different folder, e.g.,
.PP
.RS 5
mhfixmsg -outfile - | \\
.RS 0
%libdir%/rcvstore +folder
.RE
.RE
.SS Summary of Applicability
The transformations apply to the parts of a message depending on
content type and/or encoding as follows:
.PP
.RS 5
.nf
.ta \w'\-fixboundary 'u
\-decodetext   base64 and quoted-printable encoded text parts
\-textcodeset  text/plain parts
\-reformat     text parts that are not text/plain
\-fixboundary  outermost multipart part
\-fixcte       multipart part
.fi
.RE
.PP
.SS "Backup of Original Message/File"
If it applies any transformations to a message or file,
and the
.B \-outfile
switch is not used,
.B mhfixmsg
backs up the original the same way as
.BR rmm .
That is, it uses the
.I rmmproc
profile component, if present.  If not present,
.B mhfixmsg
moves the original message to a backup file.
The
.B \-rmmproc
switch may be used to override this profile component.  The
.B \-normmproc
switch disables the use of any
.I rmmproc
profile component and negates all prior
.B \-rmmproc
switches.
.PP
.SS "Integration with procmail"
By way of example, here is an excerpt from a procmailrc file
that filters messages through
.B mhfixmsg
before storing them in the user's
.I nmh-workers
folder.  It also stores the incoming message in the
.I Backups
folder in a filename generated by
.BR mktemp ,
which is a non-POSIX utility to generate a temporary file.
If you do not have that utility, then the
.BR mkstemp (3)
function could form the basis for a substitute.  Or,
.B mhfixmsg
could be called on the message after it is stored.
.PP
.RS 5
.nf
.ta \w'\-fixboundary 'u
PATH = %bindir%:$PATH
MAILDIR = `mhparam path`
MKTEMP = 'mktemp Backups/mhfixmsg.XXXXXXXX'
MHFIXMSG = 'mhfixmsg -noverbose -file - -outfile -'
STORE = %libdir%/rcvstore

:0 w: nmh-worker/procmail.$LOCKEXT
* ^TOnmh-workers@nongnu.org
| tee `$MKTEMP` | $MHFIXMSG | $STORE +nmh-workers
.fi
.RE
.PP
.SH FILES
.fc ^ ~
.nf
.ta \w'%etcdir%/mhn.defaults  'u
^$HOME/\&.mh\(ruprofile~^The user profile
^%etcdir%/mhn.defaults~^Default mhfixmsg conversion entries
.fi
.SH "PROFILE COMPONENTS"
.fc ^ ~
.nf
.ta 2.4i
.ta \w'ExtraBigProfileName  'u
^Path:~^To determine the user's nmh directory
^Current\-Folder:~^To find the default current folder
^rmmproc:~^Program to delete original messages or files
.fi
.SH "SEE ALSO"
.IR mh-profile (5),
.IR mhbuild (1),
.IR mhlist (1),
.IR mhshow (1),
.IR mkstemp (3),
.IR procmail (1),
.IR procmailrc (5),
.IR rcvstore (1),
.IR rmm (1)
.SH DEFAULTS
.nf
.RB ` +folder "' defaults to the current folder"
.RB ` msgs "' defaults to cur"
.RB ` "\-decodetext 8bit"'
.RB ` \-notextcodeset '
.RB ` \-reformat '
.RB ` \-fixboundary '
.RB ` \-fixcte '
.RB ` \-noverbose '
.fi
.SH CONTEXT
If a folder is given, it will become the current folder.  The last
message selected from a folder will become the current message.  If
the
.B \-file
switch is used, the context will not be modified.