.\" Copyright (c) 1991, 1993 .\" The Regents of the University of California. All rights reserved. .\" .\" This code is derived from software contributed to Berkeley by .\" the American National Standards Committee X3, on Information .\" Processing Systems. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. All advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" This product includes software developed by the University of .\" California, Berkeley and its contributors. .\" 4. Neither the name of the University nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" .\" @(#)isdigit.3 8.1 (Berkeley) 6/4/93 .\" $FreeBSD: src/lib/libc/locale/isdigit.3,v 1.19 2004/08/21 07:37:08 tjr Exp $ .\" .Dd August 21, 2004 .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 For single C .Va char Ns s locales (see .Xr multibyte 3 ) , the value of the argument is representable as an .Li 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 .