CTYPE(3C) Standard C Library Functions CTYPE(3C)

ctype, isalpha, isalnum, isascii, isblank, iscntrl, isdigit, islower, isprint, isspace, isupper, ispunct, isgraph, isxdigit, isalpha_l, isalnum_l, isblank_l, iscntrl_l, isdigit_l, islower_l, isprint_l, isspace_l, isupper_l, ispunct_l, isgraph_l, isxdigit_l - character handling

#include <ctype.h>
int isalpha(int c);

int isalnum(int c);

int isascii(int c);

int isblank(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);

int isalpha_l(int c, locale_t loc);

int isalnum_l(int c, locale_t loc);

int isblank_l(int c, locale_t loc);

int iscntrl_l(int c, locale_t loc);

int isdigit_l(int c, locale_t loc);

int isgraph_l(int c, locale_t loc);

int islower_l(int c, locale_t loc);

int isprint_l(int c, locale_t loc);

int ispunct_l(int c, locale_t loc);

int isspace_l(int c, locale_t loc);

int isupper_l(int c, locale_t loc);

int isxdigit_l(int c, locale_t loc);

These functions 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) and uselocale(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 functions isalnum_l(), isalpha_l(), isblank_l(), iscntrl_l, isdigit_l(), isgraph_l(), islower_l(), isprint_l(), ispunct_l(), isspace_l(), isupper_l(), and isxdigit_l() all behave identically to their counterparts without the '_l' prefix, except that instead of acting on the current locale, they perform the test on the locale specified in the argument loc.

The isascii() macro 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.

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.

isalnum()

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

isascii()

Tests for any ASCII character, code between 0 and 0177 inclusive.

isblank()

Tests whether c is a character of class blank in the current locale. This macro/function is not available to applications conforming to standards prior to SUSv3. See standards(7)

iscntrl()

Tests for any ``control character'' as defined by the character set.

isdigit()

Tests for any decimal-digit character.

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.

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.

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.

ispunct()

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

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.

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.

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.

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 or function returns non-zero if the classification is TRUE and 0 if the classification is FALSE.

See attributes(7) for descriptions of the following attributes:

ATTRIBUTE TYPE ATTRIBUTE VALUE
CSI Enabled
Interface Stability Standard
MT-Level MT-Safe

newlocale(3C), setlocale(3C), stdio(3C), uselocale(3C), ascii(7), environ(7), standards(7)

November 8, 2020 OmniOS