97 lines
4.3 KiB
HTML
97 lines
4.3 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
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<!--Converted with LaTeX2HTML 96.1-c (Feb 29, 1996) by Nikos Drakos (nikos@cbl.leeds.ac.uk), CBLU, University of Leeds -->
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<HTML>
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<!-- updated Sun Jul 14 20:10:00 MET DST 1996 by:
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Tony den Haan (tony@iaehv.nl) ftp://ftp.IAEhv.nl/pub/users/tony-->
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<HEAD>
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<TITLE>National Character Sets</TITLE>
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</HEAD>
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<BODY LANG="EN">
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<A HREF="node1.html"><IMG WIDTH=65 HEIGHT=24 ALIGN=BOTTOM ALT="contents" SRC="contents_motif.gif"></A> <BR>
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<B> Next:</B> <A HREF="node198.html">Getting smail Up and </A>
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<B>Up:</B> <A HREF="node195.html">Configuring elm</A>
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<B> Previous:</B> <A HREF="node196.html">Global elm Options</A>
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<BR> <P>
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<H2><A NAME="SECTION0015620000">National Character Sets</A></H2>
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<A NAME="mailelmcharsets"></A>
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Recently, there have been proposals to amend the RFC-822 standard to
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support various types of messages, such as plain text, binary data,
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Postscript files, etc. The set of standards and RFCs covering these
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aspects are commonly referred to as MIME, or Multipurpose Internet Mail
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Extensions. Among other things, this also lets the recipient know if a
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character set other than standard ASCII has been used when writing the
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message, for example using French accents, or German umlauts. This is
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supported by elm to some extent.
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<P>
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The character set used by internally to represent characters is
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usually referred to as ISO-8859-1, which is the name of the standard it
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conforms to. It is also known as Latin-1. Any message using characters
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from this character set should have the following line in its header:
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<PRE>
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Content-Type: text/plain; charset=iso-8859-1
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</PRE>
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The receiving system should recognize this field and take appropriate
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measures when displaying the message. The default for
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text/plain messages is a charset value of
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us-ascii.
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<P>
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To be able to display messages with character sets other than ASCII,
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elm must know how to print these characters. By default, when
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elm receives a message with a charset field other than
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us-ascii (or a content type other than text/plain,
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for that matter), it tries to display the message using a command called
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metamail. Messages that require metamail to be displayed
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are shown with an `M' in the very first column in the overview
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screen.
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<P>
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Since ' native character set is ISO-8859-1, calling
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metamail is not necessary to display messages using this
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character set. If elm is told that the display understands
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ISO-8859-1, it will not use metamail but will display the message
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directly instead. This can be done by setting the following option in
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the global elm.rc:
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<PRE>
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displaycharset = iso-8859-1
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</PRE>
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Note that you should set this options even when you are never going to
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send or receive any messages that actually contain characters other than
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ASCII. This is because people who do send such messages usually
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configure their mailer to put the proper Content-Type: field into
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the mail header by default, whether or not they are sending ASCII-only
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messages.
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<P>
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However, setting this option in elm.rc is not enough. The
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problem is that when displaying the message with its built-in pager,
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elm calls a library function for each character to determine
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whether it is printable or not. By default, this function will only
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recognize ASCII characters as printable, and display all other
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characters as ``?''. You may overcome this by setting the
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environment variable LC_CTYPE to ISO-8859-1, which
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tells the library to accept Latin-1 characters as printable. Support for
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this and other features is available since libc-4.5.8.
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<P>
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When sending messages that contain special characters from ISO-8859-1,
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you should make sure to set two more variables in the elm.rc
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file:
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<PRE>
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charset = iso-8859-1
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textencoding = 8bit
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</PRE>
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This makes elm report the character set as ISO-8859-1 in the mail
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header, and send it as an 8 bit value (the default is to strip all
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characters to 7 bit).
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<P>
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Of course, any of these options can also be set in the private
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elmrc file instead of the global one.
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<HR><A HREF="node1.html"><IMG WIDTH=65 HEIGHT=24 ALIGN=BOTTOM ALT="contents" SRC="contents_motif.gif"></A> <BR>
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<B> Next:</B> <A HREF="node198.html">Getting smail Up and </A>
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<B>Up:</B> <A HREF="node195.html">Configuring elm</A>
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<B> Previous:</B> <A HREF="node196.html">Global elm Options</A>
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<P><ADDRESS>
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<I>Andrew Anderson <BR>
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Thu Mar 7 23:22:06 EST 1996</I>
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</ADDRESS>
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</BODY>
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</HTML>
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