1.\" Copyright (c) 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" This code is derived from software contributed to Berkeley by 5.\" the American National Standards Committee X3, on Information 6.\" Processing Systems. 7.\" 8.\" Redistribution and use in source and binary forms, with or without 9.\" modification, are permitted provided that the following conditions 10.\" are met: 11.\" 1. Redistributions of source code must retain the above copyright 12.\" notice, this list of conditions and the following disclaimer. 13.\" 2. Redistributions in binary form must reproduce the above copyright 14.\" notice, this list of conditions and the following disclaimer in the 15.\" documentation and/or other materials provided with the distribution. 16.\" 3. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" @(#)isdigit.3 8.1 (Berkeley) 6/4/93 33.\" $FreeBSD$ 34.\" 35.Dd December 19, 2022 36.Dt ISDIGIT 3 37.Os 38.Sh NAME 39.Nm isdigit , 40.Nm isnumber , 41.Nm isdigit_l , 42.Nm isnumber_l 43.Nd decimal-digit character test 44.Sh LIBRARY 45.Lb libc 46.Sh SYNOPSIS 47.In ctype.h 48.Ft int 49.Fn isdigit "int c" 50.Ft int 51.Fn isnumber "int c" 52.Ft int 53.Fn isdigit_l "int c" "locale_t loc" 54.Ft int 55.Fn isnumber_l "int c" "locale_t loc" 56.Sh DESCRIPTION 57The 58.Fn isdigit 59and 60.Fn isdigit_l 61functions test for a decimal digit character. 62Regardless of locale, this includes the following characters only: 63.Bl -column \&``0''______ \&``0''______ \&``0''______ \&``0''______ \&``0''______ 64.It "\&``0''" Ta "``1''" Ta "``2''" Ta "``3''" Ta "``4''" 65.It "\&``5''" Ta "``6''" Ta "``7''" Ta "``8''" Ta "``9''" 66.El 67.Pp 68The 69.Fn isnumber 70and 71.Fn isnumber_l 72functions behave similarly to 73.Fn isdigit 74and 75.Fn isdigit_l , 76but may recognize additional characters, depending on the current locale 77setting. 78.Pp 79The value of the argument must be representable as an 80.Vt "unsigned char" 81or the value of 82.Dv EOF . 83.Pp 84The _l-suffixed versions take an explicit locale argument, whereas the 85non-suffixed versions use the current global or per-thread locale. 86.Sh RETURN VALUES 87The 88.Fn isdigit , 89.Fn isdigit_l , 90.Fn isnumber , 91and 92.Fn isnumber_l 93functions return zero if the character tests false and 94return non-zero if the character tests true. 95.Sh COMPATIBILITY 96The 97.Bx 4.4 98extension of accepting arguments outside of the range of the 99.Vt "unsigned char" 100type in locales with large character sets is considered obsolete 101and may not be supported in future releases. 102The 103.Fn iswdigit 104or 105.Fn iswdigit_l 106function should be used instead. 107.Sh SEE ALSO 108.Xr ctype 3 , 109.Xr ctype_l 3 , 110.Xr iswdigit 3 , 111.Xr iswdigit_l 3 , 112.Xr multibyte 3 , 113.Xr xlocale 3 , 114.Xr ascii 7 115.Sh STANDARDS 116The 117.Fn isdigit 118function conforms to 119.St -isoC . 120The 121.Fn isdigit_l 122function conforms to 123.St -p1003.1-2008 . 124.Sh HISTORY 125The 126.Fn isnumber 127function appeared in 128.Bx 4.4 . 129