MHFIXMSG(1)MHFIXMSG(1)NAMEmhfixmsg - rewrite MIME messages with various transformations
SYNOPSISmhfixmsg [+folder] [msgs | absolute pathname | -file file] [-decodetext
8bit/7bit | -nodecodetext] [-textcharset charset | -notextcharset]
[-reformat | -noreformat] [-replacetextplain | -noreplace‐
textplain] [-fixboundary | -nofixboundary] [-fixcte | -nofixcte]
[-outfile outfile] [-rmmproc program] [-normmproc] [-verbose |
-noverbose] [-version] [-help]
DESCRIPTIONmhfixmsg rewrites MIME messages, applying specific transformations such
as decoding of MIME-encoded message parts and repairing invalid MIME
headers.
MIME messages are specified in RFC 2045 to RFC 2049 (see mhbuild(1)).
The mhlist command is invaluable for viewing the content structure of
MIME messages. 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.
The -decodetext switch enables a transformation to decode each base64
and quoted-printable text message part to the selected 8bit or 7bit
encoding. If 7bit is selected for a base64 part but it will only fit
8bit, as defined by RFC 2045, then it will be decoded to 8bit quoted-
printable. Otherwise, if the decoded text would not fit the selected
encoding, the part is not decoded (and a message will be displayed if
-verbose is enabled).
When the -decodetext switch is enabled, each carriage return character
that precedes a linefeed character is removed from text parts encoded
in ASCII, ISO-8859-x, UTF-8, or Windows-12xx.
The -textcharset switch specifies that all text/plain parts of the mes‐
sage(s) should be converted to charset. Charset conversions require
that nmh be built with iconv(3); see the mhparam(1) man page for how
determine whether your nmh installation includes that. To convert text
parts other than text/plain, an external program can be used, via the
-reformat switch.
The -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,
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, mhfixmsg inserts that
text/plain part at the beginning of the containing multipart/alterna‐
tive part, if present. If not, it creates a multipart/alternative
part.
The -replacetextplain switch broadens the applicability of -reformat by
always replacing a corresponding text/plain part, if one exists. If
-verbose if enabled, the replacement will be shown as two steps: a
removal of the text/plain part followed by the usual insertion of a new
part.
-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
mhshow uses its mhshow-show-text/subtype entries. When 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
/usr/local/etc/nmh/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.
The -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 “bogus multipart content in mes‐
sage” error message from mhlist and other nmh programs that parse MIME
messages.
The -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 “must be encoded in 7bit, 8bit, or binary”
error message from mhlist and other nmh programs that parse MIME mes‐
sages.
The -verbose switch directs mhfixmsg to output informational message
for each transformation applied.
The -file file switch directs mhfixmsg to use the specified file as the
source message, rather than a message from a folder. Only one file
argument may be provided. The -file switch is implied if file is an
absolute pathname. If the file is “-”, then mhfixmsg accepts the
source message on the standard input stream. If the -outfile switch is
not enabled when using the standard input stream, mhfixmsg will not
produce a transformed output message.
mhfixmsg, by default, transforms the message in place. If the -outfile
switch is enabled, then mhfixmsg does not modify the input message or
file, but instead places its output in the specified file. An outfile
name of “-” specifies the standard output stream.
Combined with the -verbose switch, the -outfile switch can be used to
show what transformations mhfixmsg would apply without actually apply‐
ing them, e.g.,
mhfixmsg-outfile /dev/null -verbose
As always, this usage obeys any mhfixmsg switches in the user's pro‐
file.
-outfile can be combined with rcvstore to add a single transformed mes‐
sage to a different folder, e.g.,
mhfixmsg-outfile - | \
/usr/local/libexec/nmh/rcvstore +folder
Summary of Applicability
The transformations apply to the parts of a message depending on con‐
tent type and/or encoding as follows:
-decodetext base64 and quoted-printable encoded text parts
-textcharset text/plain parts
-reformat text parts that are not text/plain
-fixboundary outermost multipart part
-fixcte multipart part
Backup of Original Message/File
If it applies any transformations to a message or file, and the -out‐
file switch is not used, mhfixmsg backs up the original the same way as
rmm. That is, it uses the rmmproc profile component, if present. If
not present, mhfixmsg moves the original message to a backup file. The
-rmmproc switch may be used to override this profile component. The
-normmproc switch disables the use of any rmmproc profile component and
negates all prior -rmmproc switches.
Integration with inc
mhfixmsg can be used as an add-hook, as described in
/usr/local/share/doc/nmh/README-HOOKS. Note that add-hooks are called
from all nmh programs that add a message to a folder, not just inc.
Alternatively, a simple shell alias or function can be used to call
mhfixmsg immediately after a successful invocation of inc. For exam‐
ple, with bash:
alias inc='inc && mhfixmsg'
Integration with procmail
By way of example, here is an excerpt from a procmailrc file that fil‐
ters messages through mhfixmsg before storing them in the user's nmh-
workers folder. It also stores the incoming message in the Backups
folder in a filename generated by mktemp, which is a non-POSIX utility
to generate a temporary file. If you do not have that utility, then
the mkstemp(3) function could form the basis for a substitute. Or,
mhfixmsg could be called on the message after it is stored.
PATH = /usr/local/bin:$PATH
MAILDIR = `mhparam path`
MKTEMP = 'mktemp Backups/mhfixmsg.XXXXXXXX'
MHFIXMSG = 'mhfixmsg -noverbose -file - -outfile -'
STORE = /usr/local/libexec/nmh/rcvstore
:0 w: nmh-worker/procmail.$LOCKEXT
* ^TOnmh-workers@nongnu.org
| tee `$MKTEMP` | $MHFIXMSG | $STORE +nmh-workers
FILESmhfixmsg looks for mhn.defaults in multiple locations: absolute path‐
names 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
/usr/local/etc/nmh/mhn.defaults Default mhfixmsg conversion entries
PROFILE COMPONENTS
Path: To determine the user's nmh directory
Current-Folder: To find the default current folder
rmmproc: Program to delete original messages or files
SEE ALSOinc(1), iconv(3), mh-profile(5), mhbuild(1), mhlist(1), mhparam(1),
mhshow(1), mkstemp(3), procmail(1), procmailrc(5), rcvstore(1), rmm(1)DEFAULTS
`+folder' defaults to the current folder
`msgs' defaults to cur
`-decodetext 8bit'
`-notextcharset'
`-reformat'
`-noreplacetextplain'
`-fixboundary'
`-fixcte'
`-noverbose'
CONTEXT
If a folder is given, it will become the current folder. The last mes‐
sage selected from a folder will become the current message. If the
-file switch or an absolute pathname is used, the context will not be
modified.
nmh-1.6 March 16, 2014 MHFIXMSG(1)
