isalpha (3)
Leading comments
Copyright (c) 1993 by Thomas Koenig (ig25@rz.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 on...
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 functionsSYNOPSIS
#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);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
isascii():
-
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE
isblank():
-
_XOPEN_SOURCE >= 600 || _ISOC99_SOURCE ||
_POSIX_C_SOURCE >= 200112L;
or cc -std=c99
isalnum_l(), isalpha_l(), isblank_l(), iscntrl_l(), isdigit_l(), isgraph_l(), islower_l(), isprint_l(), ispunct_l(), isspace_l(), isupper_l(), isxdigit_l():
-
- Since glibc 2.10:
- _XOPEN_SOURCE >= 700
- Before glibc 2.10:
- _GNU_SOURCE
isascii_l():
-
- Since glibc 2.10:
- _XOPEN_SOURCE >= 700 && (_SVID_SOURCE || _BSD_SOURCE)
- Before glibc 2.10:
- _GNU_SOURCE
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 which isalpha() is true---letters which are neither uppercase nor lowercase.
- 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 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 (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 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.