ISALPHA(3)

NAME
isalnum, isalpha, isascii, isblank, iscntrl, isdigit, isgraph, islower, isprint, ispunct, isspace, isupper, isxdigit - character classification routines

SYNOPSIS
#include <ctype.h>

int isalnum(int c);
int isalpha(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);

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

isascii(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE
isblank(): _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE; or cc -std=c99

DESCRIPTION
These functions check whether c, which must have the value of an unsigned char or EOF, falls into a certain character class according to the current locale.

isalnum()
    checks for an alphanumeric character; it is equivalent to (isalpha(c) || isdigit(c)).

isalpha()
    checks for an alphabetic character; in the standard "C" locale, it is equivalent to (isupper(c) || islower(c)). In some locales, there may be additional characters for which isalpha() is true—letters which are neither upper case nor lower case.

isascii()
    checks whether c is a 7-bit unsigned char value that fits into the ASCII character set.

isblank()
    checks for a blank character; that is, a space or a tab.

iscntrl()
    checks for a control character.

isdigit()
    checks for a digit (0 through 9).

isgraph()
    checks for any printable character except space.

islower()
    checks for a lower-case character.

isprint()
    checks for any printable character including space.

ispunct()
    checks for any printable character which is not a space or an alphanumeric character.

isspace()
    checks for white-space characters. In the "C" and "POSIX" locales, these are: space, form-feed ('\f'), newline ('\n'), carriage return ('\r'), horizontal tab ('\t'), and vertical tab ('\v').

isupper()
    checks for an uppercase letter.

isxdigit()
    checks for a hexadecimal digits, that is, one of
    0 1 2 3 4 5 6 7 8 9 a b c d e f A B C D E F.

RETURN VALUE
The values returned are non-zero if the character c falls into the tested class, and a zero value if not.

CONFORMING TO
C99, 4.3BSD. C89 specifies all of these functions except isascii() and isblank(). isascii() is a BSD extension and is also an SVr4 extension. isblank() conforms to POSIX.1-2001 and C99 7.4.1.3.

NOTES
The details of what characters belong into which class depend on the current locale. For example, isupper() will not recognize an A-umlaut (Ä) as an uppercase letter in the default C locale.

SEE ALSO
iswalnum(3), iswalpha(3), iswblank(3), iswcntrl(3), iswdigit(3), iswgraph(3), iswlower(3), iswprint(3), iswpunct(3), iswspace(3), iswupper(3), iswxdigit(3), setlocale(3), tolower(3), toupper(3), ascii(7), locale(7)