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ISALPHA(3)						     Linux Programmer's Manual							ISALPHA(3)

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 clas- sification 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); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): isascii(): _XOPEN_SOURCE || /* Glibc since 2.19: */ _DEFAULT_SOURCE || /* Glibc versions <= 2.19: */ _SVID_SOURCE isblank(): _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L isalnum_l(), isalpha_l(), isblank_l(), iscntrl_l(), isdigit_l(), isgraph_l(), islower_l(), isprint_l(), ispunct_l(), isspace_l(), isup- per_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 ('\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. VERSIONS
isalnum_l(), isalpha_l(), isblank_l(), iscntrl_l(), isdigit_l(), isgraph_l(), islower_l(), isprint_l(), ispunct_l(), isspace_l(), isup- per_l(), isxdigit_l(), and isascii_l() are available since glibc 2.3. ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7). +---------------------------------+---------------+---------+ |Interface | Attribute | Value | +---------------------------------+---------------+---------+ |isalnum(), isalpha(), isascii(), | Thread safety | MT-Safe | |isblank(), iscntrl(), isdigit(), | | | |isgraph(), islower(), isprint(), | | | |ispunct(), isspace(), isupper(), | | | |isxdigit() | | | +---------------------------------+---------------+---------+ 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 standards require that the argument c for these functions is either EOF or a value that is representable in the type unsigned char. If the argument c is of type char, it must be cast to unsigned char, as in the following example: char c; ... res = toupper((unsigned char) c); This is necessary because char may be the equivalent of signed char, in which case a byte where the top bit is set would be sign extended when converting to int, yielding a value that is outside the range of unsigned char. The details of what characters belong to which class depend on the locale. For example, isupper() will not recognize an A-umlaut (A) 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), iswup- per(3), iswxdigit(3), newlocale(3), setlocale(3), toascii(3), tolower(3), toupper(3), uselocale(3), ascii(7), locale(7) GNU
2017-09-15 ISALPHA(3)

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