NAME

ctype, isdigit, isxdigit, islower, isupper, isalpha, isalnum, isspace, iscntrl, ispunct, isprint, isgraph, isascii − character handling

SYNOPSIS

#include <ctype.h>

int isalpha(int c);

int isupper(int c);

int islower(int c);

int isdigit(int c);

int isxdigit(int c);

int isalnum(int c);

int isspace(int c);

int ispunct(int c);

int isprint(int c);

int isgraph(int c);

int iscntrl(int c);

int isascii(int c);

DESCRIPTION

These macros classify character-coded integer values.  Each is a predicate returning non-zero for true, 0 for false.  The behavior of these macros, except isascii(), is affected by the current locale (see setlocale(3C)).  To modify the behavior, change the LC_TYPE category in setlocale(), that is, setlocale(LC_CTYPE, newlocale).  In the C locale, or in a locale where character type information is not defined, characters are classified according to the rules of the US-ASCII 7-bit coded character set. 

The macro isascii() is defined on all integer values; the rest are defined only where the argument is an int, the value of which is representable as an unsigned char, or EOF, which is defined by the <stdio.h> header and represents end-of-file. 

Functions exist for all the macros defined below.  To get the function form, the macro name must be undefined (for example, #undef isdigit). 

For macros described with Default and Standard-conforming versions, standard-conforming behavior will be provided for standard-conforming applications (see standards(5)) and for applications that define __XPG4_CHAR_CLASS__ before including <ctype.h>. 

Default

isalpha() tests for any character for which isupper() or islower() is true. 

Standard-conforming

isalpha() tests for any character for which isupper() or islower() is true, or any character that is one of the current locale-defined set of characters for which none of iscntrl(), isdigit(), ispunct(), or isspace() is true.  In C locale, isalpha() returns true only for the characters for which isupper() or islower() is true. 

isupper() tests for any character that is an upper-case letter or is one of the current locale-defined set of characters for which none of iscntrl(), isdigit(), ispunct(), isspace(), or islower() is true.  In the C locale, isupper() returns true only for the characters defined as upper-case ASCII characters. 

islower() tests for any character that is a lower-case letter or is one of the current locale-defined set of characters for which none of iscntrl(), isdigit(), ispunct(), isspace(), or isupper() is true.  In the C locale, islower() returns true only for the characters defined as lower-case ASCII characters. 

isdigit() tests for any decimal-digit character. 

Default

isxdigit() tests for any hexadecimal-digit character ([0−9], [A−F], or [a−f]). 

Standard-conforming

isxdigit() tests for any hexadecimal-digit character ([0−9], [A−F], or [a−f] or the current locale-defined sets of characters representing the hexadecimal digits 10 to 15 inclusive).  In the C locale, only          0 1 2 3 4 5 6 7 8 9 A B C D E F a b c d e f are included.

isalnum() tests for any character for which isalpha() or isdigit() is true (letter or digit). 

isspace() tests for any space, tab, carriage-return, newline, vertical-tab or form-feed (standard white-space characters) or for one of the current locale-defined set of characters for which isalnum() is false.  In the C locale, isspace() returns true only for the standard white-space characters. 

ispunct() tests for any printing character which is neither a space ("") nor a character for which isalnum() or iscntrl() is true. 

Default

isprint() tests for any character for which ispunct(), isupper(), islower(), isdigit(), and the space character ("") is true.

Standard-conforming

isprint() tests for any character for which iscntrl() is false, and isalnum(), isgraph(), ispunct(), the space character (""), and the characters in the current locale-defined "print" class are true.

Default

isgraph() tests for any character for which ispunct(), isupper(), islower(), and isdigit() is true. 

Standard-conforming

isgraph() tests for any character for which isalnum() and ispunct() are true, or any character in the current locale-defined "graph" class which is neither a space ("") nor a character for which iscntrl() is true. 

iscntrl() tests for any “control character” as defined by the character set. 

isascii() tests for any ASCII character, code between 0 and 0177 inclusive. 

RETURN VALUES

If the argument to any of the character handling macros is not in the domain of the function, the result is undefined.  Otherwise, the macro/function will return non-zero if the classification is TRUE, and 0 for FALSE.

FILES

/usr/lib/locale/locale/LC_CTYPE

ATTRIBUTES

See attributes(5) for descriptions of the following attributes:

SEE ALSO

setlocale(3C), stdio(3S), ascii(5), environ(5), standards(5)

NOTES

isdigit(), isxdigit(), islower(), isupper(), isalpha(), isalnum(), isspace(), iscntrl(), ispunct(), isprint(), isgraph() and isascii() can be used safely in a multi-thread application, as long as setlocale(3C) is not being called to change the locale. 

SunOS 5.6  —  Last change: 26 Feb 1997