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():
	   _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 (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.

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(),	 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 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),  isw-
       graph(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)

COLOPHON
       This  page  is  part of release 4.10 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/.



GNU				  2016-10-08			    ISALPHA(3)