preconv  -  convert  encoding  of  input  files  to something GNU troff


   preconv [-dr] [-e encoding] [files ...]
   preconv -h | --help
   preconv -v | --version

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


   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
   hexadecimal number with four to  six  digits,  representing  a  Unicode
   input  code.   Normally,  preconv  should be invoked with the -k and -K
   options of groff.


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

          Specify default encoding if everything fails (see below).

          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.

   -h     Print help message.

   -r     Do not add .lf requests.

   -v     Print version number.


   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
   variable 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
   emitted;  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
   possible to guess the right input encoding with the help  of  heuristic
   algorithms  for  data  which  represents  a greater amount of a natural
   language, it is still just a guess.  Additionally, all algorithms  fail
   easily  for  input  which  is  either  too short or doesn't represent a
   natural 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
   Variables.   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,

   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
   implementation; a call to 'preconv --version' shows  whether  iconv  is


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


   the GNU Emacs and XEmacs info pages


   Copyright  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
   permission notice identical to this one.

   Permission  is  granted  to  copy  and  distribute translations of this
   manual into another language, under the above conditions  for  modified
   versions,  except  that  this  permission  notice  may  be  included in
   translations approved by the Free Software Foundation instead of in the
   original English.


Personal Opportunity - Free software gives you access to billions of dollars of software at no cost. Use this software for your business, personal use or to develop a profitable skill. Access to source code provides access to a level of capabilities/information that companies protect though copyrights. Open source is a core component of the Internet and it is available to you. Leverage the billions of dollars in resources and capabilities to build a career, establish a business or change the world. The potential is endless for those who understand the opportunity.

Business Opportunity - Goldman Sachs, IBM and countless large corporations are leveraging open source to reduce costs, develop products and increase their bottom lines. Learn what these companies know about open source and how open source can give you the advantage.

Free Software

Free Software provides computer programs and capabilities at no cost but more importantly, it provides the freedom to run, edit, contribute to, and share the software. The importance of free software is a matter of access, not price. Software at no cost is a benefit but ownership rights to the software and source code is far more significant.

Free Office Software - The Libre Office suite provides top desktop productivity tools for free. This includes, a word processor, spreadsheet, presentation engine, drawing and flowcharting, database and math applications. Libre Office is available for Linux or Windows.

Free Books

The Free Books Library is a collection of thousands of the most popular public domain books in an online readable format. The collection includes great classical literature and more recent works where the U.S. copyright has expired. These books are yours to read and use without restrictions.

Source Code - Want to change a program or know how it works? Open Source provides the source code for its programs so that anyone can use, modify or learn how to write those programs themselves. Visit the GNU source code repositories to download the source.


Study at Harvard, Stanford or MIT - Open edX provides free online courses from Harvard, MIT, Columbia, UC Berkeley and other top Universities. Hundreds of courses for almost all major subjects and course levels. Open edx also offers some paid courses and selected certifications.

Linux Manual Pages - A man or manual page is a form of software documentation found on Linux/Unix operating systems. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts.