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.\"     @(#)isdigit.3	8.1 (Berkeley) 6/4/93
.\" $FreeBSD: src/lib/libc/locale/isdigit.3,v 1.25 2009/09/04 07:44:58 des Exp $
.\"
.Dd May 4, 2007
.Dt ISDIGIT 3
.Os
.Sh NAME
.Nm isdigit, isnumber
.Nd decimal-digit character test
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In ctype.h
.Ft int
.Fn isdigit "int c"
.Ft int
.Fn isnumber "int c"
.Sh DESCRIPTION
The
.Fn isdigit
function tests for a decimal digit character.
Regardless of locale, this includes the following characters only:
.Pp
.Bl -column \&``0''______ \&``0''______ \&``0''______ \&``0''______ \&``0''______
.It "\&``0''\t``1''\t``2''\t``3''\t``4''"
.It "\&``5''\t``6''\t``7''\t``8''\t``9''"
.El
.Pp
The
.Fn isnumber
function behaves similarly to
.Fn isdigit ,
but may recognize additional characters, depending on the current locale
setting.
.Pp
The value of the argument must be representable as an
.Vt "unsigned char"
or the value of
.Dv EOF .
.Sh RETURN VALUES
The
.Fn isdigit
and
.Fn isnumber
functions return zero if the character tests false and
return non-zero if the character tests true.
.Sh COMPATIBILITY
The
.Bx 4.4
extension of accepting arguments outside of the range of the
.Vt "unsigned char"
type in locales with large character sets is considered obsolete
and may not be supported in future releases.
The
.Fn iswdigit
function should be used instead.
.Sh SEE ALSO
.Xr ctype 3 ,
.Xr isalnum_l 3 ,
.Xr iswdigit 3 ,
.Xr multibyte 3 ,
.Xr ascii 7
.Sh STANDARDS
The
.Fn isdigit
function conforms to
.St -isoC .
.Sh HISTORY
The
.Fn isnumber
function appeared in
.Bx 4.4 .