ctype(3C)ctype(3C)NAME
ctype: isalnum(), isalpha(), isascii(), isblank(), iscntrl(),
isdigit(), isgraph(), islower(), isprint(), ispunct(), isspace(), isup‐
per(), isxdigit() - classify characters according to type
SYNOPSISDESCRIPTION
These functions classify character-coded integer values according to
the rules of the coded character set identified by the last successful
call to (see setlocale(3C)). Each function is a predicate returning
nonzero for true, zero for false.
If has not been called successfully, characters are classified accord‐
ing to the rules of the default ASCII 7-bit coded character set (see
setlocale(3C)).
is defined on all integer values; the other functions are defined for
the range (EOF) through
RETURN VALUE
The functions return nonzero under the following circumstances; zero
otherwise:
c is an alphanumeric (letters or digits).
c is a letter.
c is any ASCII character code between 0 and
0177, inclusive.
c is a blank character; that is, a space or a
tab.
c is a control character (in ASCII: character
codes less than 040 and the delete character
(0177)).
c is a decimal digit (in ASCII: characters
[0-9]).
c is a visible character (in ASCII: printing
characters, excluding the space character
(040)).
c is a lowercase letter.
c is a printing character.
c is a punctuation character (in ASCII: any
printing character except the space charac‐
ter (040), digits, letters).
c is a character that creates whitespace in
displayed text (in ASCII: space, tab, car‐
riage return, newline, vertical tab, and
formfeed).
c is an uppercase letter.
c is a hexadecimal digit (in ASCII: characters
[0-9], [A-F] or [a-f]).
If the argument to any of these functions is outside the domain of the
function, the result is undefined.
EXTERNAL INFLUENCES
Environment Variables
The category determines the classification of character type.
International Code Set Support
Single-byte character code sets are supported.
WARNINGS
These functions are supplied both as library functions and as macros
defined in the header. Normally, the macro versions are used. To
obtain the library function, either use a to remove the macro defini‐
tion or, if compiling in ANSI-C mode, enclose the function name in
parenthesis or take its address. The following example uses the
library functions for and
AUTHOR
was developed by IBM, OSF, and HP.
SEE ALSOsetlocale(3C), ascii(5), thread_safety(5).
STANDARDS CONFORMANCEctype(3C)