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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 - 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);

   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

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 (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 upper case nor lower case.

       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 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),  isw-
       graph(3),  iswlower(3),  iswprint(3),  iswpunct(3), iswspace(3), iswup-
       per(3), iswxdigit(3), setlocale(3), toascii(3), tolower(3), toupper(3),
       ascii(7), locale(7)

COLOPHON
       This  page  is  part of release 3.27 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                               2010-09-20                        ISALPHA(3)

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