Linux "preconv" Command Line Options and Examples
convert encoding of input files to something GNU troff understands
preconv reads files and converts its encoding(s) to a form GNU troff(1) can process, sending the data to stan‐ dard 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.
preconv [-dr] [-e encoding] [files ...]
preconv -h | --help
preconv -v | --version
Command Line Options:
Emit debugging messages to standard error (mainly the used encoding).
preconv -d ...
Specify default encoding if everything fails (see below).
preconv -Dencoding ...
Specify input encoding explicitly, overriding all other methods. This corresponds to groff's -Kencod‐ing option. Without this switch, preconv uses the algorithm described below to select the input encod‐ing.
preconv -eencoding ...
Print help message.
preconv -h ...
Do not add .lf requests.
preconv -r ...
USAGEpreconv 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 inputline. 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 tooption -k.Byte Order MarkThe Unicode Standard defines character U+FEFF as the Byte Order Mark (BOM). On the other hand, value U+FFFEis 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 streamstarts with U+FEFF. Similarly, the data stream encoded as ‘UTF-8’ might start with a BOM (to ease the conver‐sion from and to UTF-16 and UTF-32). In all cases, the byte order mark is not part of the data but part ofthe 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 ‘zerowidth no-break space’ character – something not needed normally in groff.Coding TagsEditors which support more than a single character encoding need tags within the input files to mark thefile's encoding. While it is possible to guess the right input encoding with the help of heuristic algorithmsfor data which represents a greater amount of a natural language, it is still just a guess. Additionally, allalgorithms 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 Emacsand XEmacs (and probably other programs too).Coding tags in GNU Emacs and XEmacs are stored in so-called File Variables. preconv recognizes the followingsyntax form which must be put into a troff comment in the first or second line.
preconv -v ...
The only relevant tag for preconv is ‘coding’ which can take the values listed below. Here an example linewhich 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 listis 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-16leIn addition, the following hard-coded list of other tags is recognized which eventually map to values from thelist 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-signatureThose tags are taken from GNU Emacs and XEmacs, together with some aliases. Trailing ‘-dos’, ‘-unix’, and
preconv -*- ...