Index for Section 3

Alphabetical listing for C

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ctype(3)
NAME
  isalnum, isalpha, isascii, iscntrl, isdigit, isgraph, islower, isprint,
  ispunct, isspace, isupper, isxdigit - Classify characters

LIBRARY
  Standard C Library (libc)

SYNOPSIS
  #include <ctype.h>

  int isalnum(
	  int c);

  int isalpha(
	  int c);

  int isascii(
	  int c);

  int iscntrl(
	  int c);

  int isdigit(
	  int c);

  int isgraph(
	  int c);

  int islower(
	  int c);

  int isprint(
	  int c);

  int ispunct(
	  int c);

  int isspace(
	  int c);

  int isupper(
	  int c);

  int isxdigit(
	  int c);

STANDARDS
  Interfaces documented on this reference page conform to industry standards
  as follows:

  isalnum(), isalpha(), isascii(), iscntrl(), isdigit(), isgraph(),
  islower(), isprint(), ispunct(), isspace(), isupper(), isxdigit(): XSH5.0

  Refer to the standards(5) reference page for more information about
  industry standards and associated tags.

PARAMETERS
  c	    Specifies the character to be tested. In all cases, this
	    parameter is an  int data type, whose value must be representable
	    as an unsigned char or must equal the value of the macro EOF
	    (defined in the stdio.h include file). When this parameter has a
	    value that cannot be represented as an unsigned char or EOF, the
	    result is undefined.

DESCRIPTION
  The ctype functions test for membership in a character class in the current
  locale.  Each function tests to see if a character is part of a different
  character class.

  If the character is part of the character class, the function returns a
  nonzero value for true; otherwise, the function returns a value of 0 (zero)
  for false.

  Each function is named by adding the prefix is to the name of the character
  class for which the function tests. For example, the isalpha() function
  tests whether the character specified by the c parameter belongs to the
  alpha class.

  The following lists the function names and describes the conditions under
  which the functions return a true value.

  isalnum() When c is a character of class alpha or class digit in the
	    program's current locale.

  isalpha() When c is a character of class alpha in the program's current
	    locale. Characters in classes lower and upper automatically
	    belong to class alpha.

  isascii() When c is a 7-bit US-ASCII character whose value is in the range
	    0 to 0177 (0 to 0x7F), inclusive.

  iscntrl() When c is a character of class cntrl in the program's current
	    locale.

  isdigit() When c is a character of class digit in the program's current
	    locale. The following characters are included in this class:


		 0 1 2 3 4 5 6 7 8 9

  isgraph() When c is a character of class graph in the program's current
	    locale. Characters in classes alpha, digit, and punct are
	    automatically in class graph.  Unlike isprint(), isgraph()
	    returns FALSE for the space character.

  islower() When c is a character of class lower in the program's current
	    locale. At a minimum, the 26 lowercase US-ASCII characters are
	    included in this class. These are:


		 a b c d e f g h i j k l m n o p q r s t u v w x y z

  isprint() When c is a character of class print in the program's current
	    locale. All characters in the class graph and the space character
	    are automatically included in the class print.

  ispunct() When c is a character of class punct in the program's current
	    locale.

  isspace() When c is a character of class space in the program's current
	    locale. At a minimum, the space, form-feed, newline, carriage-
	    return, tab, and vertical-tab characters are included in this
	    class.

  isupper() When c is a character of class upper in the program's current
	    locale. At a minimum, the 26 uppercase US-ASCII characters are
	    included in this class. These are:


		 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

  isxdigit()
	    When c is a character of class xdigit in the program's current
	    locale. The following characters are included in this class:


		 0 1 2 3 4 5 6 7 8 9 A B C D E F a b c d e f

NOTES
  The LC_CTYPE category of the current locale affects all conversions.

  In the C locale, or in a locale where character-type information is not
  defined, characters are classified according to the rules of the ASCII
  character set.  For any character value greater than octal 177 (0177 in C-
  language context) the value 0 (zero) is returned.

  [Tru64 UNIX]	The isdigit(), isxdigit(), and isalnum() functions do not
  recognize Thai digits. Many applications make assumptions about how a digit
  character can be converted to its numeric equivalent.	 Changing the
  functions to recognize Thai digits would break these applications. Refer to
  TACTIS(5) for more information about Thai digits.

RETURN VALUES
  Upon successful completion of any function, a nonzero (TRUE) value is
  returned.  Otherwise, the value 0 (FALSE) is returned.

RELATED INFORMATION
  Files: locale(4)

  Functions: ctype(3), setlocale(3), wctype(3)

  Standards: i18n_intro(5), standards(5)

Index for Section 3

Alphabetical listing for C

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