preconv(1)
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.
Opportunity
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.
Education
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.
