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

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);

   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(), 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 (isal‐
	      pha(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.

ATTRIBUTES
   Multithreading (see pthreads(7))
       The  isalnum(),	isalpha(), isascii(), isblank(), iscntrl(), isdigit(),
       isgraph(), islower(), isprint(), ispunct(), isspace(),  isupper(),  and
       isxdigit() functions are thread-safe.

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.

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(),	 iscn‐
       trl_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),  isw‐
       graph(3),  iswlower(3),	iswprint(3),  iswpunct(3), iswspace(3), iswup‐
       per(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 3.63 of the Linux man-pages project.  A
       description of the project, and information about reporting  bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.

GNU				  2014-03-18			    ISALPHA(3)
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