Manual page for ctype(3C)
ctype, isdigit, isxdigit, islower, isupper, isalpha, isalnum, isspace, iscntrl, ispunct, isprint, isgraph, isascii - character handling
SYNOPSIS
#include <ctype.h>
int isalpha(int c);
int isupper(int c);
int islower(int c);
int isdigit(int c);
int isxdigit(int c);
int isalnum(int c);
int isspace(int c);
int ispunct(int c);
int isprint(int c);
int isgraph(int c);
int iscntrl(int c);
int isascii(int c);
DESCRIPTION
These macros classify character-coded integer values.
Each is a predicate returning non-zero for true,
0
for false.
The behavior of these macros, except
isascii(),
is affected
by the current locale (see
setlocale.3c
To modify the behavior, change the
LC_TYPE
category in
setlocale(),
that is,
setlocale(LC_CTYPE, newlocale).
In the
C
locale, or in a locale where character type information is not
defined, characters are classified according to the rules of the
US-ASCII
7-bit coded character set.
The macro
isascii()
is defined on all integer values;
the rest are defined only where the argument is an
int,
the value of which is representable as an
unsigned char,
or
EOF,
which is defined by the
<stdio.h>
header and represents end-of-file.
Functions exist for all the macros defined below.
To get the function
form, the macro name must be undefined (for example, #undef isdigit).
For macros described with
Default
and
Standard-conforming
versions, standard-conforming behavior will be provided for
standard-conforming applications (see
standards.5
and for applications that define
__XPG4_CHAR_CLASS__
before including
<ctype.h>.
Default
- isalpha()
-
tests for any character for which
isupper()
or
islower()
is true.
Standard-conforming
- isalpha()
-
tests for any character for which
isupper()
or
islower()
is true, or any character that is one of the current locale-defined set
of characters for which none of
iscntrl(),
isdigit(),
ispunct(),
or
isspace()
is true.
In
C
locale,
isalpha()
returns true only for the characters for which
isupper()
or
islower()
is true.
- isupper()
-
tests for any character that is an upper-case letter or is one of the
current locale-defined set of characters for which none of
iscntrl(),
isdigit(),
ispunct(),
isspace(),
or
islower()
is true.
In the
C
locale,
isupper()
returns true only
for the characters defined as upper-case
ASCII
characters.
- islower()
-
tests for any character that is a lower-case letter or is one of the
current locale-defined set of characters for which none of
iscntrl(),
isdigit(),
ispunct(),
isspace(),
or
isupper()
is true.
In the
C
locale,
islower()
returns true only
for the characters defined as lower-case ASCII characters.
- isdigit()
-
tests for any decimal-digit character.
Default
- isxdigit()
-
tests for any hexadecimal-digit character ([0-9],
[A-F], or [a-f]).
Standard-conforming
- isxdigit()
-
tests for any hexadecimal-digit character ([0-9],
[A-F], or [a-f] or the current locale-defined
sets of characters representing the hexadecimal digits
10
to
15
inclusive).
In the
C
locale, only
0 1 2 3 4 5 6 7 8 9 A B C D E F a b c d e f
are included.
- isalnum()
-
tests for any character for which
isalpha()
or
isdigit()
is true (letter or digit).
- isspace()
-
tests for any space, tab, carriage-return, newline,
vertical-tab or form-feed (standard white-space characters)
or for one of the current locale-defined set of characters for which
isalnum()
is false. In the C locale,
isspace()
returns true only for the standard white-space characters.
- ispunct()
-
tests for any printing character which is neither a space
("") nor
a character for which
isalnum()
or
iscntrl()
is true.
Default
- isprint()
-
tests for any character for which
ispunct(),
isupper(),
islower(),
isdigit(),
and the space character ("") is true.
Standard-conforming
- isprint()
-
tests for any character for which
iscntrl()
is false, and
isalnum(),
isgraph(),
ispunct(),
the space character (""),
and the characters in the current locale-defined
"print" class are true.
Default
- isgraph()
-
tests for any character for which
ispunct(),
isupper(),
islower(),
and
isdigit()
is true.
Standard-conforming
- isgraph()
-
tests for any character for which
isalnum()
and
ispunct()
are true, or any character in the current
locale-defined "graph" class which is neither a space ("")
nor a character for which
iscntrl()
is true.
- iscntrl()
-
tests for any ``control character'' as defined by the character set.
- isascii()
-
tests for any ASCII character,
code between 0 and 0177 inclusive.
RETURN VALUES
If the argument to any of the character handling macros
is not in the domain of the function, the result is undefined.
Otherwise, the macro/function will return non-zero if the
classification is
TRUE,
and
0
for
FALSE.
FILES
/usr/lib/locale/locale/LC_CTYPE
ATTRIBUTES
See
attributes.5
for descriptions of the following attributes:
+---------------+-------------------------+
|ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+---------------+-------------------------+
|MT-Level | MT-Safe with exceptions |
|CSI | Enabled |
+---------------+-------------------------+
SEE ALSO
setlocale.3c
stdio.3s
ascii.5
environ.5
standards.5
NOTES
isdigit(),
isxdigit(),
islower(),
isupper(),
isalpha(),
isalnum(),
isspace(),
iscntrl(),
ispunct(),
isprint(),
isgraph()
and
isascii()
can be used safely in a multi-thread application, as long as
setlocale.3c
is not being called to change the locale.
Created by unroff & hp-tools.
© by Hans-Peter Bischof. All Rights Reserved (1997).
Last modified 07/October/97
