Name
isalnum, isalpha, isascii, isblank, iscntrl, isdigit, isgraph, islower, isprint, ispunct, isspace, isupper, isxdigit, isalnum_l, isalpha_l, isascii_l, isblank_l, iscntrl_l, isdigit_l, isgraph_l, islower_l, isprint_l, ispunct_l, isspace_l, isupper_l, isxdigit_l — character classification functions
Synopsis
#include <ctype.h>
int
isalnum( |
int c); |
int
isalpha( |
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); |
int
isascii( |
int c); |
int
isblank( |
int c); |
int
isalnum_l( |
int c, |
locale_t locale); |
int
isalpha_l( |
int c, |
locale_t locale); |
int
isblank_l( |
int c, |
locale_t locale); |
int
iscntrl_l( |
int c, |
locale_t locale); |
int
isdigit_l( |
int c, |
locale_t locale); |
int
isgraph_l( |
int c, |
locale_t locale); |
int
islower_l( |
int c, |
locale_t locale); |
int
isprint_l( |
int c, |
locale_t locale); |
int
ispunct_l( |
int c, |
locale_t locale); |
int
isspace_l( |
int c, |
locale_t locale); |
int
isupper_l( |
int c, |
locale_t locale); |
int
isxdigit_l( |
int c, |
locale_t locale); |
int
isascii_l( |
int c, |
locale_t locale); |
![[Note]](../stylesheet/note.png) |
Note | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
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 specified locale. The functions without the
"_l" suffix perform the check based on the current
locale.
The functions with the "_l" suffix perform the check based
on the locale specified by the locale object locale. The behavior of these
functions is undefined if locale is the special locale
object LC_GLOBAL_LOCALE (see
duplocale(3)) or is not a
valid locale object handle.
The list below explains the operation of the functions
without the "_l" suffix; the functions with the "_l" suffix
differ only in using the locale object locale instead of 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 whichisalpha() is true—letters which are neither uppercase nor lowercase. isascii()-
checks whether
cis 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 lowercase 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 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 nonzero if the character
c falls into the
tested class, and zero if not.
ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7).
| Interface | Attribute | Value |
isalnum(), isalpha(), isascii(), isblank(), iscntrl(), isdigit(), isgraph(), islower(), isprint(), ispunct(), isspace(), isupper(), isxdigit() |
Thread safety | MT-Safe |
VERSIONS
isalnum_l(), isalpha_l(), isblank_l(), iscntrl_l(), isdigit_l(), isgraph_l(), islower_l(), isprint_l(), ispunct_l(), isspace_l(), isupper_l(), isxdigit_l(), and isascii_l() are available since glibc
2.3.
CONFORMING TO
C89 specifies isalnum(),
isalpha(), iscntrl(), isdigit(), isgraph(), islower(), isprint(), ispunct(), isspace(), isupper(), and isxdigit(), but not isascii() and isblank(). POSIX.1-2001 also specifies
those functions, and also isascii() (as an XSI extension) and
isblank(). C99 specifies all of
the preceding functions, except isascii().
POSIX.1-2008 marks isascii()
as obsolete, noting that it cannot be used portably in a
localized application.
POSIX.1-2008 specifies isalnum_l(), isalpha_l(), isblank_l(), iscntrl_l(), isdigit_l(), isgraph_l(), islower_l(), isprint_l(), ispunct_l(), isspace_l(), isupper_l(), and isxdigit_l().
isascii_l() is a GNU
extension.
NOTES
The details of what characters belong to which class
depend on the 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), newlocale(3), setlocale(3), uselocale(3), toascii(3), tolower(3), toupper(3), ascii(7), locale(7)
COLOPHON
This page is part of release 4.07 of the Linux man-pages project. A
description of the project, information about reporting bugs,
and the latest version of this page, can be found at
https://www.kernel.org/doc/man−pages/.
|
Copyright (c) 1993 by Thomas Koenig (ig25rz.uni-karlsruhe.de) %%%LICENSE_START(VERBATIM) Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Since the Linux kernel and libraries are constantly changing, this manual page may be incorrect or out-of-date. The author(s) assume no responsibility for errors or omissions, or for damages resulting from the use of the information contained herein. The author(s) may not have taken the same level of care in the production of this manual, which is licensed free of charge, as they might when working professionally. Formatted or processed versions of this manual, if unaccompanied by the source, must acknowledge the copyright and authors of this work. %%%LICENSE_END Modified Sat Jul 24 19:10:00 1993 by Rik Faith (faithcs.unc.edu) Modified Sun Aug 21 17:51:50 1994 by Rik Faith (faithcs.unc.edu) Modified Sat Sep 2 21:52:01 1995 by Jim Van Zandt <jrvvanzandt.mv.com> Modified Mon May 27 22:55:26 1996 by Martin Schulze (joeylinux.de) |