xenial (1) preconv.1.gz

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NAME

       preconv - convert encoding of input files to something GNU troff understands

SYNOPSIS

       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.

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
       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.

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 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, 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
       implementation; 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 © 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.