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


NAME


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

SYNOPSIS


#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);

DESCRIPTION


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(5)


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.


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

ATTRIBUTES


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

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

SEE ALSO


newlocale(3C), setlocale(3C), uselocale(3C), stdio(3C), ascii(5),
environ(5), standards(5)


March 14, 2016 CTYPE(3C)