Introduction to libiconv
For historical reasons, international text is often encoded using a language or country dependent character encoding. With the advent of the internet and the frequent exchange of text across countries - even the viewing of a web page from a foreign country is a "text exchange" in this context -, conversions between these encodings have become important. They have also become a problem, because many characters which are present in one encoding are absent in many other encodings. To solve this mess, the Unicode encoding has been created. It is a super-encoding of all others and is therefore the default encoding for new text formats like XML.Still, many computers still operate in locale with a traditional (limited) character encoding. Some programs, like mailers and web browsers, must be able to convert between a given text encoding and the user's encoding. Other programs internally store strings in Unicode, to facilitate internal processing, and need to convert between internal string representation (Unicode) and external string representation (a traditional encoding) when they are doing I/O. GNU libiconv is a conversion library for both kinds of applications.
Details
This library provides aniconv()
implementation, for use on systems which don't have one, or whose implementation cannot convert from/to Unicode.
It provides support for the encodings:
- European languages
- ASCII, ISO-8859-{1,2,3,4,5,7,9,10,13,14,15,16}, KOI8-R, KOI8-U, KOI8-RU, CP{1250,1251,1252,1253,1254,1257}, CP{850,866,1131}, Mac{Roman,CentralEurope,Iceland,Croatian,Romania}, Mac{Cyrillic,Ukraine,Greek,Turkish}, Macintosh
- Semitic languages
- ISO-8859-{6,8}, CP{1255,1256}, CP862, Mac{Hebrew,Arabic}
- Japanese
- EUC-JP, SHIFT_JIS, CP932, ISO-2022-JP, ISO-2022-JP-2, ISO-2022-JP-1
- Chinese
- EUC-CN, HZ, GBK, CP936, GB18030, EUC-TW, BIG5, CP950, BIG5-HKSCS, BIG5-HKSCS:2004, BIG5-HKSCS:2001, BIG5-HKSCS:1999, ISO-2022-CN, ISO-2022-CN-EXT
- Korean
- EUC-KR, CP949, ISO-2022-KR, JOHAB
- Armenian
- ARMSCII-8
- Georgian
- Georgian-Academy, Georgian-PS
- Tajik
- KOI8-T
- Kazakh
- PT154, RK1048
- Thai
- ISO-8859-11, TIS-620, CP874, MacThai
- Laotian
- MuleLao-1, CP1133
- Vietnamese
- VISCII, TCVN, CP1258
- Platform specifics
- HP-ROMAN8, NEXTSTEP
- Full Unicode
- UTF-8
UCS-2, UCS-2BE, UCS-2LE
UCS-4, UCS-4BE, UCS-4LE
UTF-16, UTF-16BE, UTF-16LE
UTF-32, UTF-32BE, UTF-32LE
UTF-7
C99, JAVA - Full Unicode, in terms of
uint16_t
oruint32_t
(with machine dependent endianness and alignment) - UCS-2-INTERNAL, UCS-4-INTERNAL
- Locale dependent, in terms of `char' or `wchar_t' (with machine dependent endianness and alignment, and with OS and locale dependent semantics)
- char, wchar_t
The empty encoding name "" is equivalent to "char": it denotes the locale dependent character encoding.
--enable-extra-encodings
, it also provides support for a few extra encodings:
- European languages
- CP{437,737,775,852,853,855,857,858,860,861,863,865,869,1125}
- Semitic languages
- CP864
- Japanese
- EUC-JISX0213, Shift_JISX0213, ISO-2022-JP-3
- Chinese
- BIG5-2003 (experimental)
- Turkmen
- TDS565
- Platform specifics
- ATARIST, RISCOS-LATIN1
It has also some limited support for transliteration, i.e. when a character cannot be represented in the target character set, it can be approximated through one or several similarly looking characters. Transliteration is activated when "//TRANSLIT" is appended to the target encoding name.
libiconv is for you if your application needs to support multiple character encodings, but that support lacks from your system.
Installation
As usual for GNU packages:$ ./configure --prefix=/usr/local $ make $ make install
After installing GNU libiconv for the first time, it is recommended to recompile and reinstall GNU gettext, so that it can take advantage of libiconv.
On systems other than GNU/Linux, the iconv program will be internationalized only if GNU gettext has been built and installed before GNU libiconv. This means that the first time GNU libiconv is installed, we have a circular dependency between the GNU libiconv and GNU gettext packages, which can be resolved by building and installing either
- first libiconv, then gettext, then libiconv again,
- first gettext, then libiconv, then gettext again.
This library can be built and installed in two variants:
- The library mode. This works on all systems, and uses a library
libiconv.so
and a header file<iconv.h>
. (Both are installed through "make install".)To use it, simply
#include <iconv.h>
and use the functions.To use it in an autoconfiguring package:
- If you don't use automake, append
m4/iconv.m4
to youraclocal.m4
file. - If you do use automake, add
m4/iconv.m4
to your m4 macro repository. - Add to the link command line of libraries and executables that use the functions the placeholder
@LIBICONV@
(or, if using libtool for the link,@LTLIBICONV@
). If you use automake, the right place for these additions are the *_LDADD variables.
iconv.m4
is also part of the GNU gettext package, which installs it in/usr/local/share/aclocal/iconv.m4
. - If you don't use automake, append
- The libc plug/override mode. This works on GNU/Linux, Solaris and OSF/1 systems only. It is a way to get good iconv support without having glibc-2.1. It installs a library
preloadable_libiconv.so
. This library can be used with LD_PRELOAD, to override the iconv* functions present in the C library.- On GNU/Linux and Solaris:
$ export LD_PRELOAD=/usr/local/lib/preloadable_libiconv.so
- On OSF/1:
$ export _RLD_LIST=/usr/local/lib/preloadable_libiconv.so:DEFAULT
- On GNU/Linux and Solaris:
Copyright
Thelibiconv
and libcharset
libraries and
their header files are under LGPL.
The iconv
program is under GPL.
Downloading libiconv
libiconv can be found on in the subdirectory/pub/gnu/libiconv/
on your favorite GNU
mirror. For other ways to obtain libiconv, please read How to get GNU
Software.
The latest release is http://ftp.gnu.org/pub/gnu/libiconv/libiconv-1.14.tar.gz
The latest development sources can be obtained through the savannah project.
Documentation
Below are the links for the online documentation.- The
iconv
program - iconv.1.html
- The library functions
- iconv_open.3.html
iconv.3.html
iconv_close.3.html
iconvctl.3.html
iconv_open_into.3.html