SYNOPSIS

     #include <ctype.h>

     int
     isdigit(int c);

     int
     isnumber(int c);

DESCRIPTION

     The isdigit() function tests for a decimal digit character.  Regardless
     of locale, this includes the following characters only:

     ``0''         ``1''         ``2''         ``3''         ``4''
     ``5''         ``6''         ``7''         ``8''         ``9''

     The isnumber() function behaves similarly to isdigit(), but may recognize
     additional characters, depending on the current locale setting.

     For single C chars locales (see multibyte(3)) the value of the argument
     is representable as an unsigned char or the value of EOF.

RETURN VALUES

     The isdigit() and isnumber() functions return zero if the character tests
     false and returns non-zero if the character tests true.

COMPATIBILITY

     The 4.4BSD extension of accepting arguments outside of the range of the
     unsigned char type in locales with large character sets is considered
     obsolete and may not be supported in future releases.  The iswdigit()
     function should be used instead.

SEE ALSO

     ctype(3), iswdigit(3), multibyte(3), ascii(7), isalnum_l

STANDARDS

     The isdigit() function conforms to ISO/IEC 9899:1990 (``ISO C90'').

HISTORY

     The isnumber() function appeared in 4.4BSD.

BSD                             August 21, 2004                            BSD