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preconv(1)                                                          preconv(1)




NAME

       preconv - convert encoding of input files to something GNU troff under-
       stands


SYNOPSIS

       [files ...]  -h | --help -v | --version

       It is possible to have whitespace between the -e  command  line  option
       and its parameter.


DESCRIPTION

       preconv reads files and converts its encoding(s) to a form GNU troff(1)
       can process, sending the data  to  standard  output.   Currently,  this
       means ASCII characters and `\[uXXXX]' entities, where `XXXX' is a hexa-
       decimal number with four to six digits, representing  a  Unicode  input
       code.   Normally,  preconv should be invoked with the -k and -K options
       of groff.


OPTIONS

       -d     Emit debugging messages  to  standard  error  (mainly  the  used
              encoding).

       -Dencoding
              Specify default encoding if everything fails (see below).

       -eencoding
              Specify input encoding explicitly, overriding all other methods.
              This corresponds to groff's  -Kencoding  option.   Without  this
              switch, preconv uses the algorithm described below to select the
              input encoding.

       --help -h Print help message.

       -r     Do not add .lf requests.

       --version
              -v Print version number.


USAGE

       preconv tries to find the input encoding with the following  algorithm.

       1.     If  the input encoding has been explicitly specified with option
              -e, use it.

       2.     Otherwise, check whether the input starts with a Byte Order Mark
              (BOM, see below).  If found, use it.

       3.     Finally,  check  whether there is a known coding tag (see below)
              in either the first or second input line.  If found, use it.

       4.     If everything fails, use a default encoding as given with option
              -D,  by  the current locale, or `latin1' if the locale is set to
              `C', `POSIX', or empty (in that order).

       Note that the groff program supports a GROFF_ENCODING environment vari-
       able which is eventually expanded to option -k.

   Byte Order Mark
       The  Unicode  Standard  defines character U+FEFF as the Byte Order Mark
       (BOM).  On the other hand, value U+FFFE is guaranteed not be a  Unicode
       character at all.  This allows to detect the byte order within the data
       stream (either big-endian or  lower-endian),  and  the  MIME  encodings
       `UTF-16'  and `UTF-32' mandate that the data stream starts with U+FEFF.
       Similarly, the data stream encoded as `UTF-8' might start  with  a  BOM
       (to  ease the conversion from and to UTF-16 and UTF-32).  In all cases,
       the byte order mark is not part of the data but part  of  the  encoding
       protocol; in other words, preconv's output doesn't contain it.

       Note  that  U+FEFF not at the start of the input data actually is emit-
       ted; it has then the meaning of a `zero width no-break space' character
       - something not needed normally in groff.

   Coding Tags
       Editors  which  support more than a single character encoding need tags
       within the input files to mark the file's encoding.  While it is possi-
       ble  to guess the right input encoding with the help of heuristic algo-
       rithms for data which represents a greater amount  of  a  natural  lan-
       guage,  it  is  still  just a guess.  Additionally, all algorithms fail
       easily for input which is either too short or doesn't represent a natu-
       ral language.

       For  these  reasons,  preconv  supports the coding tag convention (with
       some restrictions) as used by GNU Emacs and XEmacs (and probably  other
       programs too).

       Coding  tags in GNU Emacs and XEmacs are stored in so-called File Vari-
       ables.  preconv recognizes the following syntax form which must be  put
       into a troff comment in the first or second line.

              -*- tag1: value1; tag2: value2; ... -*-

       The only relevant tag for preconv is `coding' which can take the values
       listed below.  Here an example line which tells Emacs to edit a file in
       troff mode, and to use latin2 as its encoding.

              .\" -*- mode: troff; coding: latin-2 -*-

       The  following  list  gives  all  MIME coding tags (either lowercase or
       uppercase) supported by preconv; this list is hard-coded in the source.

              big5, cp1047, euc-jp, euc-kr, gb2312, iso-8859-1, iso-8859-2,
              iso-8859-5, iso-8859-7, iso-8859-9, iso-8859-13, iso-8859-15,
              koi8-r, us-ascii, utf-8, utf-16, utf-16be, utf-16le

       In  addition, the following hard-coded list of other tags is recognized
       which eventually map to values from the list above.

              ascii, chinese-big5, chinese-euc, chinese-iso-8bit, cn-big5,
              cn-gb, cn-gb-2312, cp878, csascii, csisolatin1,
              cyrillic-iso-8bit, cyrillic-koi8, euc-china, euc-cn, euc-japan,
              euc-japan-1990, euc-korea, greek-iso-8bit, iso-10646/utf8,
              iso-10646/utf-8, iso-latin-1, iso-latin-2, iso-latin-5,
              iso-latin-7, iso-latin-9, japanese-euc, japanese-iso-8bit, jis8,
              koi8, korean-euc, korean-iso-8bit, latin-0, latin1, latin-1,
              latin-2, latin-5, latin-7, latin-9, mule-utf-8, mule-utf-16,
              mule-utf-16be, mule-utf-16-be, mule-utf-16be-with-signature,
              mule-utf-16le, mule-utf-16-le, mule-utf-16le-with-signature,
              utf8, utf-16-be, utf-16-be-with-signature,
              utf-16be-with-signature, utf-16-le, utf-16-le-with-signature,
              utf-16le-with-signature

       Those tags are taken from GNU Emacs  and  XEmacs,  together  with  some
       aliases.   Trailing `-dos', `-unix', and `-mac' suffixes of coding tags
       (which give the end-of-line convention used in the file)  are  stripped
       off before the comparison with the above tags happens.

   Iconv Issues
       preconv  by  itself only supports three encodings: latin-1, cp1047, and
       UTF-8; all other encodings are passed to the iconv  library  functions.
       At  compile time it is searched and checked for a valid iconv implemen-
       tation; a call to `preconv --version' shows whether iconv is used.


BUGS

       preconv doesn't support local variable lists yet.  This is a  different
       syntax form to specify local variables at the end of a file.


SEE ALSO

       groff(1)
       the GNU Emacs and XEmacs info pages


COPYING

       Copyright (C) 2006-2014 Free Software Foundation, Inc.

       Permission  is  granted  to make and distribute verbatim copies of this
       manual provided the copyright notice and  this  permission  notice  are
       preserved on all copies.

       Permission  is granted to copy and distribute modified versions of this
       manual under the conditions for verbatim  copying,  provided  that  the
       entire  resulting derived work is distributed under the terms of a per-
       mission notice identical to this one.

       Permission is granted to copy and distribute translations of this  man-
       ual into another language, under the above conditions for modified ver-
       sions, except that this permission notice may be included  in  transla-
       tions approved by the Free Software Foundation instead of in the origi-
       nal English.



Groff Version 1.22.3            4 November 2014                     preconv(1)

groff 1.22.3 - Generated Tue Oct 13 07:44:08 CDT 2015
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