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(libc.info)Character Handling

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Character Handling
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   Programs that work with characters and strings often need to
classify a character--is it alphabetic, is it a digit, is it
whitespace, and so on--and perform case conversion operations on
characters.  The functions in the header file `ctype.h' are provided
for this purpose.

   Since the choice of locale and character set can alter the
classifications of particular character codes, all of these functions
are affected by the current locale.  (More precisely, they are affected
by the locale currently selected for character classification--the
`LC_CTYPE' category; see Note: Locale Categories.)

   The ISO C standard specifies two different sets of functions.  The
one set works on `char' type characters, the other one on `wchar_t'
wide characters (Note: Extended Char Intro).

Classification of Characters

Testing whether characters are

letters, digits, punctuation, etc.

Case Conversion

Case mapping, and the like.

Classification of Wide Characters

Character class determination for

wide characters.

Using Wide Char Classes

Notes on using the wide character

classes.

Wide Character Case Conversion

Mapping of wide characters.