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 

       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 featuretestmacros(7)):

       isascii():
           BSDSOURCE || SVIDSOURCE || XOPENSOURCE
       isblank():
           XOPENSOURCE >= 600 || ISOC99SOURCE ||
           POSIXCSOURCE >= 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.

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()                        │               │         │
       └──────────────────────────────────┴───────────────┴─────────┘
VERSIONS
       isalnuml(),   isalphal(),   isblankl(),   iscntrll(),  isdigitl(),
       isgraphl(), islowerl(), isprintl(), ispunctl(), isspacel(),  isup‐
       perl(), isxdigitl(), and isasciil() are available since glibc 2.3.

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 3.53 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)