isalnum, isalpha, isascii, isblank, iscntrl, isdigit, isgraph, islower, isprint,
ispunct, isspace, isupper, isxdigit - character classification routines
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);
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.
- checks for an alphanumeric character; it is equivalent to
(isalpha(c) || isdigit(c)).
- 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.
- checks whether c is a 7-bit unsigned char value that fits
into the ASCII character set. This function is a BSD extension and is also
an SVID extension.
- checks for a blank character; that is, a space or a tab. This function is
a GNU extension.
- checks for a control character.
- checks for a digit (0 through 9).
- checks for any printable character except space.
- checks for a lower-case character.
- checks for any printable character including space.
- checks for any printable character which is not a space or an alphanumeric
- 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').
- checks for an uppercase letter.
- checks for a hexadecimal digits, i.e. one of 0 1 2 3 4 5 6 7 8 9 a b c
d e f A B C D E F.
The values returned are nonzero if the character c falls into the tested
class, and a zero value if not.
ANSI - C, BSD 4.3. isascii() is a BSD extension and is also an SVID
extension. isblank() is a GNU extension.
The details of what characters belong into which class depend on the current
locale. For example, isupper() will not recognize an A - umlaut as an
uppercase letter in the default C locale.