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Introduction to libunistring

Text files are nowadays usually encoded in Unicode, and may consist of very different scripts – from Latin letters to Chinese Hanzi –, with many kinds of special characters – accents, right-to-left writing marks, hyphens, Roman numbers, and much more. But the POSIX platform APIs for text do not contain adequate functions for dealing with particular properties of many Unicode characters. In fact, the POSIX APIs for text have several assumptions at their base which don't hold for Unicode text.

This library provides functions for manipulating Unicode strings and for manipulating C strings according to the Unicode standard.


This library consists of the following parts:

<unistr.h>   elementary string functions
<uniconv.h>   conversion from/to legacy encodings
<unistdio.h>   formatted output to strings
<uniname.h>   character names
<unictype.h>   character classification and properties
<uniwidth.h>   string width when using nonproportional fonts
<uniwbrk.h>   word breaks
<unilbrk.h>   line breaking algorithm
<uninorm.h>   normalization (composition and decomposition)
<unicase.h>   case folding
<uniregex.h>   regular expressions (not yet implemented)

Who needs libunistring?

libunistring is for you if your application involves non-trivial text processing, such as upper/lower case conversions, line breaking, operations on words, or more advanced analysis of text. Text provided by the user can, in general, contain characters of all kinds of scripts. The text processing functions provided by this library handle all scripts and all languages.

libunistring is for you if your application already uses the ISO C / POSIX <ctype.h>, <wctype.h> functions and the text it operates on is provided by the user and can be in any language.

libunistring is also for you if your application uses Unicode strings as internal in-memory representation.


The online manual is available at

Downloading libunistring

libunistring can be downloaded from For other ways to obtain libunistring, please read How to get GNU Software.

The latest development sources can be obtained through the savannah project.

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Last updated: $Date: 2024/02/24 16:01:08 $ $Author: haible $