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  (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 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 charac-
              ter.

       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().  isas-
       cii() 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), iswgraph(3), iswlower(3),
       iswprint(3),    iswpunct(3),   iswspace(3),   iswupper(3),   iswxdigit(3),   setlocale(3),
       toascii(3), tolower(3), toupper(3), ascii(7), locale(7)

COLOPHON
       This page is part of release 3.53 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)