Chapter 11. Data conversion

	Tip
	iconv(1) is provided as a part of the libc6 package and it is always available on practically all Unix-like systems to convert the encoding of characters.

You can convert encodings of a text file with iconv(1) by the following.

$ iconv -f encoding1 -t encoding2 input.txt >output.txt

Encoding values are case insensitive and ignore "-" and "_" for matching. Supported encodings can be checked by the "iconv -l" command.

	Note
	Some encodings are only supported for the data conversion and are not used as locale values (Section 8.3.1, “Basics of encoding”).

For character sets which fit in single byte such as ASCII and ISO-8859 character sets, the character encoding means almost the same thing as the character set.

For character sets with many characters such as JIS X 0213 for Japanese or Universal Character Set (UCS, Unicode, ISO-10646-1) for practically all languages, there are many encoding schemes to fit them into the sequence of the byte data.

For these, there are clear differentiations between the character set and the character encoding.

The code page is used as the synonym to the character encoding tables for some vendor specific ones.

Note

Please note most encoding systems share the same code with ASCII for the 7 bit characters. But there are some exceptions. If you are converting old Japanese C programs and URLs data from the casually-called shift-JIS encoding format to UTF-8 format, use "CP932" as the encoding name instead of "shift-JIS" to get the expected results: 0x5C → "\" and 0x7E → "~". Otherwise, these are converted to wrong characters.

	Tip
	recode(1) may be used too and offers more than the combined functionality of iconv(1), fromdos(1), todos(1), frommac(1), and tomac(1). For more, see "info recode".

#!/bin/sh
ENCDN=iso-8859-1
for x in *;
 do
 mv "$x" "$(echo "$x" | iconv -f $ENCDN -t utf-8)"
done

The "$ENCDN" variable specifies the original encoding used for file names under older OS as in Table 11.2, “List of encoding values and their usage”.

For more complicated case, please mount a filesystem (e.g. a partition on a disk drive) containing such file names with proper encoding as the mount(8) option (see Section 8.3.6, “Filename encoding”) and copy its entire contents to another filesystem mounted as UTF-8 with "cp -a" command.

$ vim u-file.txt

$ vim '+e ++enc=latin2 pu-file.txt'

$ vim '+e ++enc=eucJP ju-file.txt'

$ vim '+e ++enc=CP932 ++ff=dos jw-file.txt'

Please refer to the mbyte.txt "multi-byte text support" in vim on-line help and Table 11.2, “List of encoding values and their usage” for locale values used with "++enc".

The emacs family of programs can perform the equivalent functions.

XML text looks somewhat like HTML. It enables us to manage multiple formats of output for a document. One easy XML system is the docbook-xsl package, which is used here.

Each XML file starts with standard XML declaration as the following.

<?xml version="1.0" encoding="UTF-8"?>

The basic syntax for one XML element is marked up as the following.

<name attribute="value">content</name>

XML element with empty content is marked up in the following short form.

<name attribute="value"/>

The "attribute="value"" in the above examples are optional.

The comment section in XML is marked up as the following.

<!-- comment -->

Other than adding markups, XML requires minor conversion to the content using predefined entities for following characters.

	Caution
	"<" or "&" can not be used in attributes or elements.

	Note
	When SGML style user defined entities, e.g. "&some-tag:", are used, the first definition wins over others. The entity definition is expressed in "<!ENTITY some-tag "entity value">".

	Note
	As long as the XML markup are done consistently with certain set of the tag name (either some data as content or attribute value), conversion to another XML is trivial task using Extensible Stylesheet Language Transformations (XSLT).

There are many tools available to process XML files such as the Extensible Stylesheet Language (XSL).

Basically, once you create well formed XML file, you can convert it to any format using Extensible Stylesheet Language Transformations (XSLT).

The Extensible Stylesheet Language for Formatting Objects (XSL-FO) is supposed to be solution for formatting. The fop package is new to the Debian main archive due to its dependence to the Java programing language. So the LaTeX code is usually generated from XML using XSLT and the LaTeX system is used to create printable file such as DVI, PostScript, and PDF.

Since XML is subset of Standard Generalized Markup Language (SGML), it can be processed by the extensive tools available for SGML, such as Document Style Semantics and Specification Language (DSSSL).

	Tip
	GNOME's yelp is sometimes handy to read DocBook XML files directly since it renders decently on X.

Traditionally, roff is the main Unix text processing system. See roff(7), groff(7), groff(1), grotty(1), troff(1), groff_mdoc(7), groff_man(7), groff_ms(7), groff_me(7), groff_mm(7), and "info groff".

You can read or print a good tutorial and reference on "-me" macro in "/usr/share/doc/groff/" by installing the groff package.

	Tip
	"groff -Tascii -me -" produces plain text output with ANSI escape code. If you wish to get manpage like output with many "^H" and "_", use "GROFF_NO_SGR=1 groff -Tascii -me -" instead.

	Tip
	To remove "^H" and "_" from a text file generated by groff, filter it by "col -b -x".

The TeX Live software distribution offers a complete TeX system. The texlive metapackage provides a decent selection of the TeX Live packages which should suffice for the most common tasks.

There are many references available for TeX and LaTeX.

This is the most powerful typesetting environment. Many SGML processors use this as their back end text processor. Lyx provided by the lyx package and GNU TeXmacs provided by the texmacs package offer nice WYSIWYG editing environment for LaTeX while many use Emacs and Vim as the choice for the source editor.

There are many online resources available.

When documents become bigger, sometimes TeX may cause errors. You must increase pool size in "/etc/texmf/texmf.cnf" (or more appropriately edit "/etc/texmf/texmf.d/95NonPath" and run update-texmf(8)) to fix this.

Note

The TeX source of "The TeXbook" is available at http://tug.ctan.org/tex-archive/systems/knuth/dist/tex/texbook.tex. This file contains most of the required macros. I heard that you can process this document with tex(1) after commenting lines 7 to 10 and adding "\input manmac \proofmodefalse". It's strongly recommended to buy this book (and all other books from Donald E. Knuth) instead of using the online version but the source is a great example of TeX input!

Although writing a manual page (manpage) in the plain troff format is possible, there are few helper packages to create it.

The core of printable data manipulation is the Ghostscript PostScript (PS) interpreter which generates raster image.

The latest upstream Ghostscript from Artifex was re-licensed from AFPL to GPL and merged all the latest ESP version changes such as CUPS related ones at 8.60 release as unified release.

	Tip
	"gs -h" can display the configuration of Ghostscript.

You can merge two PostScript (PS) or Portable Document Format (PDF) files using gs(1) of Ghostscript.

$ gs -q -dNOPAUSE -dBATCH -sDEVICE=pswrite -sOutputFile=bla.ps -f foo1.ps foo2.ps
$ gs -q -dNOPAUSE -dBATCH -sDEVICE=pdfwrite -sOutputFile=bla.pdf -f foo1.pdf foo2.pdf

	Note
	The PDF, which is a widely used cross-platform printable data format, is essentially the compressed PS format with few additional features and extensions.

	Tip
	For command line, psmerge(1) and other commands from the psutils package are useful for manipulating PostScript documents. pdftk(1) from the pdftk package is useful for manipulating PDF documents, too.

Both lp(1) and lpr(1) commands offered by Common Unix Printing System (CUPS) provides options for customized printing the printable data.

You can print 3 copies of a file collated using one of the following commands.

$ lp -n 3 -o Collate=True filename

$ lpr -#3 -o Collate=True filename

You can further customize printer operation by using printer option such as "-o number-up=2", "-o page-set=even", "-o page-set=odd", "-o scaling=200", "-o natural-scaling=200", etc., documented at Command-Line Printing and Options.

Mail (SMTP) data should be limited to series of 7 bit data. So binary data and 8 bit text data are encoded into 7 bit format with the Multipurpose Internet Mail Extensions (MIME) and the selection of the charset (see Section 8.3.1, “Basics of encoding”).

The standard mail storage format is mbox formatted according to RFC2822 (updated RFC822). See mbox(5) (provided by the mutt package).

For European languages, "Content-Transfer-Encoding: quoted-printable" with the ISO-8859-1 charset is usually used for mail since there are not much 8 bit characters. If European text is encoded in UTF-8, "Content-Transfer-Encoding: quoted-printable" is likely to be used since it is mostly 7 bit data.

For Japanese, traditionally "Content-Type: text/plain; charset=ISO-2022-JP" is usually used for mail to keep text in 7 bits. But older Microsoft systems may send mail data in Shift-JIS without proper declaration. If Japanese text is encoded in UTF-8, Base64 is likely to be used since it contains many 8 bit data. The situation of other Asian languages is similar.

	Note
	If your non-Unix mail data is accessible by a non-Debian client software which can talk to the IMAP4 server, you may be able to move them out by running your own IMAP4 server (see Section 6.7, “POP3/IMAP4 server”).

	Note
	If you use other mail storage formats, moving them to mbox format is the good first step. The versatile client program such as mutt(1) may be handy for this.

You can split mailbox contents to each message using procmail(1) and formail(1).

Each mail message can be unpacked using munpack(1) from the mpack package (or other specialized tools) to obtain the MIME encoded contents.