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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 <&lt;ctype.h>&gt;

       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; 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 non-zero 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.

NOTES
       The  details  of  what characters belong into which class depend on the
       current locale.  For example, isupper() will not recognize an  A-umlaut
       () 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), tolower(3), toupper(3), ascii(7),
       locale(7)

COLOPHON
       This page is part of release 3.05 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                               2007-07-26                        ISALPHA(3)