mh, MH - Introduction to the MH system for handling mail
MH is the name of a powerful message handling system.
Rather than being a single comprehensive program, MH consists
of a collection of fairly simple single-purpose programs
to send, receive, save, and retrieve messages.
Unlike mail, MH is not a closed system that must be
explicitly run, and then exited when you wish to return to
the shell. Instead, you may freely intersperse MH commands
with other shell commands. This allows you to read and
answer your mail while you have (for example) a compilation
running, or are searching for a file or running programs
to find an answer to someone's question before
replying to them.
To get started using MH, add the directory /usr/bin/mh to
your $PATH. This is best done in one of the files or in
your home directory. Check the reference page for the
shell you use if you do not know how to do this. Run the
inc command. If you have never used MH before, the inc
command creates the necessary default files and directories
after asking you if you want it to do so. The inc
command moves mail from your system maildrop into your MH
+inbox folder. Each message is converted to MH format,
and stored as separate files in your +inbox folder until
you have read it. When you have read a message, you can
refile it in another folder that you have created.
Folders are directories in which messages are stored: the
folders themselves are stored in your Mail directory. See
refile(1) and folder(1) for more details.
For each message it processes, inc prints a one-line display.
The one-line display contains the From: field, the
Subject: field, and as much of the first line of the message
as it can accommodate. The first message that inc
processes becomes your current message. All MH commands
operate on the current message unless you have specified
the msg argument.
You need to run inc each time you wish to incorporate new
mail into your +inbox folder.
The scan command prints a list of the messages in your
current folder.
The commands show, next, and prev are used to read specific
messages from the current folder. Of these, show
displays the current message. You can also display a specific
message by specifying its number. In the following
example, the mail system displays the contents of message
number 10 in the current folder:
% show 10
The commands next and prev display the message numerically
following and numerically preceding the current message,
respectively. In all cases, the message displayed becomes
the current message. If there is no current message, show
may be called with an argument, or next may be used to
advance to the first message. The command rmm (remove message)
deletes the current message.
You can delete messages other than the current message by
specifying the message number or numbers. When you specify
more than one message, you separate each message number by
a space. In the following example, messages 2, 4 and 6 in
the current folder are deleted:
% rmm 2 4 6
The command repl is used to reply to a message. This command
places you in the editor with a prototype response
form. While you are in the editor, you may view the item
you are responding to by reading the file @.
The comp command allows you to compose a message by
putting you in the editor on a blank message header form,
and then lets you send it.
All the MH commands can be run with only the -help option,
which causes them to print a list of the parameters and
options with which they can be used.
Commands that take a message number as an argument (scan,
show, and repl, for example) also take one of the following
keywords: Specifies the first message in the current
folder. Specifies the last message in the current folder.
Specifies the current message in the current folder.
Specifies the previous message in the current folder.
Specifies the next message in the current folder.
Commands that take a range of message numbers, such as
rmm, scan, or show, also take any of the following abbreviations:
Indicates all messages in the range num1 to
num2, inclusive. The specified range must contain at least
one message. Indicate up to n messages beginning with (or
ending with) message num. The value of num may be any of
the MH message keywords: first, prev, cur, next, or last.
Specify the first, previous, next, or last n messages, if
they exist.
MH software offers many other options, such as creating
multiple folders for different topics, and automatically
refiling messages according to subject, source, destination,
or content. The following MH reference pages provide
information on the specified topics: Extracting addresses
from message headers Listing mail aliases Annotating messages
Exploding digests into messages Composing a message
Redistributing a message to additional addresses Setting/listing
the current folder/message Listing all folders
Forwarding messages Incorporating new mail Marking
messages Producing formatted listings of MH messages Sending
or reading mail Printing full pathnames of MH messages
and folders Checking for messages Running the MH shell
Showing the next message Compressing a folder into a single
file Selecting messages by content Showing the previous
message Prompting editor front end Incorporating new
mail asynchronously Filing messages in other folders
Replying to a message Removing a folder Removing messages
Producing a one line per message scan listing Sending a
message Receiving mail hooks Showing (listing) messages
Sorting messages Using the prompting front-end for send
Reporting who will receive a message when it is sent Using
the alias file for the MH message system Using the format
file for the MH message system Using the message format
file for the MH message system Using the user customization
for the MH message system Using the systemwide customization
for the MH message system Running the program
that parses addresses in RFC 822-style Searching for
alias/password conflicts Running the program that parses
dates in RFC 822-style Initializing the MH environment for
a system Running the backend processor for the send command
Internationalization (I18N) Features [Toc] [Back]
The default mail interchange code in the United States is
based on using only 7 bits of each byte to represent each
character. To provide full support for European languages
other than English, MH software must reserve the full 8
bits of each byte for character representation. Support
for 8-bit code in mail is enabled by the system manager as
part of the configuration process for worldwide support
software.
In Asian countries, there are a variety of coded character
sets (codesets) that are used for interchange of mail
between systems and for processing by local applications.
Most of these codesets require more than one byte to represent
each character. For Asian languages, the MH software
therefore supports codeset conversion of mail messages
between the mail interchange codeset and the user's
application codeset. For example, if the mail interchange
codeset at sites in Japan is ISO-2022-JP and the user's
application codeset is eucJP, the next command needs to
convert the next message to eucJP before displaying the
message. Otherwise, Japanese characters do not display
correctly.
Codeset conversion is controlled through entries in various
files, command options, and variable settings that are
associated with MH software. The conversion is actually
done by converters that reside in the
/usr/lib/nls/loc/iconv directory. Each converter supports
a single from_code and to_code conversion that is identified
in the converter name. For example, the converter
that supports conversion from the ISO-2022-JP mail interchange
codeset to the eucJP user application codeset is
named ISO-2022-JP_eucJP. Codeset conversion works only if
converters are available for the mail interchange and user
application codesets that apply to the message and if
those converters are installed. (Converters are installed
from optional language-specific subsets). Refer to the
iconv_intro(5) reference page for more information about
codeset conversion.
By default, to eliminate risk of data loss, the inc command
stores incoming mail messages in mail folders without
codeset conversion. In this case, the codeset conversion
is performed later when you display or extract messages
from mail folders. If you want codeset conversion to be
performed at the time messages are stored in folders, you
can specify the -conv option on the inc command line. To
ensure correct codeset conversion in some Asian countries,
you may need to use the inc -conv inshdr command when
incoming messages do not include a Content-Type entry in
the header. Refer to the inc(1) reference page for more
information on the -conv option.
To include mail interchange codeset information in outgoing
mail messages, the MH software adds new header lines.
For example, if ISO-2022-JP is the mail interchange code,
the following header lines are added to outgoing messages:
Mime-Version: 1.0 Content-Type: TEXT/PLAIN;
charset=ISO-2022-JP
For non-ISO codesets, the software adds the prefix "X-" to
the codeset name for identification purposes. For example,
if the codeset is eucJP, the following header lines are
added to the message:
Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=XeucJP
For incoming mail, MH software uses the following settings
(in the order listed) to determine the mail interchange
codeset: The value specified for charset in the ContentType:
header line, if present in the incoming message The
default systemwide mail interchange codeset as specified
in the /usr/lib/mail-codesets file
This file must be created by the system administrator
and contains one line that is the name of the
systemwide mail interchange codeset. For example:
ISO-2022-JP
When parsing the mail-codesets file, the MH software
ignores comment lines (lines beginning with
#), blank lines, and leading or trailing white
space around the codeset name. The first line that
is not a comment or blank line is assumed to specify
the systemwide mail interchange codeset.
The MH software does not perform codeset conversion on
incoming mail if neither of these settings specifies a
codeset.
For outgoing mail, MH software uses the following settings
(in the order listed) to determine the mail interchange
codeset: The EXCODE environment variable The profile component
excode defined in $HOME/.mh_profile The content of
/usr/lib/mail-codesets
MH software determines the user application codeset from
the codeset part of locale name settings for the following
variables and file entries (listed in order of high to low
precedence): The LC_ALL environment variable The LANG
environment variable The profile component lang defined in
$HOME/.mh_profile
You cannot create folder names that are made up of only
digits.
Directory containing commands MH library
mh(1)
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