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); |
![[Note]](../stylesheet/note.png) |
Note | |||||
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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 whichisalpha() is true—letters which are neither upper case nor lower case. 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 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, 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 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
isascii() as obsolete, noting
that it cannot be used portably in a localized
application.
NOTES
The details of what characters belong into which class
depend on the current 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), setlocale(3), toascii(3), tolower(3), toupper(3), ascii(7), locale(7)
COLOPHON
This page is part of release 3.33 of the Linux man-pages project. A
description of the project, and information about reporting
bugs, can be found at http://man7.org/linux/man-pages/.
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Copyright (c) 1993 by Thomas Koenig (ig25rz.uni-karlsruhe.de) 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. 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) |