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.\" 34.Dd December 19, 2022 35.Dt ISDIGIT 3 36.Os 37.Sh NAME 38.Nm isdigit , 39.Nm isnumber , 40.Nm isdigit_l , 41.Nm isnumber_l 42.Nd decimal-digit character test 43.Sh LIBRARY 44.Lb libc 45.Sh SYNOPSIS 46.In ctype.h 47.Ft int 48.Fn isdigit "int c" 49.Ft int 50.Fn isnumber "int c" 51.Ft int 52.Fn isdigit_l "int c" "locale_t loc" 53.Ft int 54.Fn isnumber_l "int c" "locale_t loc" 55.Sh DESCRIPTION 56The 57.Fn isdigit 58and 59.Fn isdigit_l 60functions test for a decimal digit character. 61Regardless of locale, this includes the following characters only: 62.Bl -column \&``0''______ \&``0''______ \&``0''______ \&``0''______ \&``0''______ 63.It "\&``0''" Ta "``1''" Ta "``2''" Ta "``3''" Ta "``4''" 64.It "\&``5''" Ta "``6''" Ta "``7''" Ta "``8''" Ta "``9''" 65.El 66.Pp 67The 68.Fn isnumber 69and 70.Fn isnumber_l 71functions behave similarly to 72.Fn isdigit 73and 74.Fn isdigit_l , 75but may recognize additional characters, depending on the current locale 76setting. 77.Pp 78The value of the argument must be representable as an 79.Vt "unsigned char" 80or the value of 81.Dv EOF . 82.Pp 83The _l-suffixed versions take an explicit locale argument, whereas the 84non-suffixed versions use the current global or per-thread locale. 85.Sh RETURN VALUES 86The 87.Fn isdigit , 88.Fn isdigit_l , 89.Fn isnumber , 90and 91.Fn isnumber_l 92functions return zero if the character tests false and 93return non-zero if the character tests true. 94.Sh COMPATIBILITY 95The 96.Bx 4.4 97extension of accepting arguments outside of the range of the 98.Vt "unsigned char" 99type in locales with large character sets is considered obsolete 100and may not be supported in future releases. 101The 102.Fn iswdigit 103or 104.Fn iswdigit_l 105function should be used instead. 106.Sh SEE ALSO 107.Xr ctype 3 , 108.Xr ctype_l 3 , 109.Xr iswdigit 3 , 110.Xr iswdigit_l 3 , 111.Xr multibyte 3 , 112.Xr xlocale 3 , 113.Xr ascii 7 114.Sh STANDARDS 115The 116.Fn isdigit 117function conforms to 118.St -isoC . 119The 120.Fn isdigit_l 121function conforms to 122.St -p1003.1-2008 . 123.Sh HISTORY 124The 125.Fn isnumber 126function appeared in 127.Bx 4.4 . 128