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);
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. This function is a BSD
extension and is also an SVID extension.
- isblank()
- checks for a blank character; that is, a space or a tab.
This function is a GNU extension.
- 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, 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.
RETURN VALUE¶
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.
NOTE¶
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.
SEE ALSO¶
tolower(3),
toupper(3),
setlocale(3),
ascii(7),
locale(7)