#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);
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.
#include <the> C
and
POSIX
locales, these are: space, form-feed
(aq\faq),
newline
(aq\naq),
carriage return
(aq\raq),
horizontal tab
(aq\taq),
and vertical tab
(aq\vaq).
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.
POSIX.1-2008 marks
isalpa()
as obsolete.
NOTES
The details of what characters belong into which class depend on the current
locale.
For example,
isupper()
will not recognize an A-umlaut (:A) as an uppercase letter in the default
C
locale.
This page is part of release 3.14 of the Linux
man-pages
project.
A description of the project,
and information about reporting bugs,
can be found at
http://www.kernel.org/doc/man-pages/.
