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.Dd December 19, 2022 33.Dt ISDIGIT 3 34.Os 35.Sh NAME 36.Nm isdigit , 37.Nm isnumber , 38.Nm isdigit_l , 39.Nm isnumber_l 40.Nd decimal-digit character test 41.Sh LIBRARY 42.Lb libc 43.Sh SYNOPSIS 44.In ctype.h 45.Ft int 46.Fn isdigit "int c" 47.Ft int 48.Fn isnumber "int c" 49.Ft int 50.Fn isdigit_l "int c" "locale_t loc" 51.Ft int 52.Fn isnumber_l "int c" "locale_t loc" 53.Sh DESCRIPTION 54The 55.Fn isdigit 56and 57.Fn isdigit_l 58functions test for a decimal digit character. 59Regardless of locale, this includes the following characters only: 60.Bl -column \&``0''______ \&``0''______ \&``0''______ \&``0''______ \&``0''______ 61.It "\&``0''" Ta "``1''" Ta "``2''" Ta "``3''" Ta "``4''" 62.It "\&``5''" Ta "``6''" Ta "``7''" Ta "``8''" Ta "``9''" 63.El 64.Pp 65The 66.Fn isnumber 67and 68.Fn isnumber_l 69functions behave similarly to 70.Fn isdigit 71and 72.Fn isdigit_l , 73but may recognize additional characters, depending on the current locale 74setting. 75.Pp 76The value of the argument must be representable as an 77.Vt "unsigned char" 78or the value of 79.Dv EOF . 80.Pp 81The _l-suffixed versions take an explicit locale argument, whereas the 82non-suffixed versions use the current global or per-thread locale. 83.Sh RETURN VALUES 84The 85.Fn isdigit , 86.Fn isdigit_l , 87.Fn isnumber , 88and 89.Fn isnumber_l 90functions return zero if the character tests false and 91return non-zero if the character tests true. 92.Sh COMPATIBILITY 93The 94.Bx 4.4 95extension of accepting arguments outside of the range of the 96.Vt "unsigned char" 97type in locales with large character sets is considered obsolete 98and may not be supported in future releases. 99The 100.Fn iswdigit 101or 102.Fn iswdigit_l 103function should be used instead. 104.Sh SEE ALSO 105.Xr ctype 3 , 106.Xr ctype_l 3 , 107.Xr iswdigit 3 , 108.Xr iswdigit_l 3 , 109.Xr multibyte 3 , 110.Xr xlocale 3 , 111.Xr ascii 7 112.Sh STANDARDS 113The 114.Fn isdigit 115function conforms to 116.St -isoC . 117The 118.Fn isdigit_l 119function conforms to 120.St -p1003.1-2008 . 121.Sh HISTORY 122The 123.Fn isnumber 124function appeared in 125.Bx 4.4 . 126