1.\" $OpenBSD: isdigit.3,v 1.14 2023/01/20 17:21:12 millert Exp $ 2.\" 3.\" Copyright (c) 1991 The Regents of the University of California. 4.\" Copyright (c) 2017 Ingo Schwarze <schwarze@openbsd.org> 5.\" All rights reserved. 6.\" 7.\" This code is derived from software contributed to Berkeley by 8.\" the American National Standards Committee X3, on Information 9.\" Processing Systems. 10.\" 11.\" Redistribution and use in source and binary forms, with or without 12.\" modification, are permitted provided that the following conditions 13.\" are met: 14.\" 1. Redistributions of source code must retain the above copyright 15.\" notice, this list of conditions and the following disclaimer. 16.\" 2. Redistributions in binary form must reproduce the above copyright 17.\" notice, this list of conditions and the following disclaimer in the 18.\" documentation and/or other materials provided with the distribution. 19.\" 3. Neither the name of the University nor the names of its contributors 20.\" may be used to endorse or promote products derived from this software 21.\" without specific prior written permission. 22.\" 23.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 24.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 25.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 26.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 27.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 28.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 29.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 30.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 32.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33.\" SUCH DAMAGE. 34.\" 35.Dd $Mdocdate: January 20 2023 $ 36.Dt ISDIGIT 3 37.Os 38.Sh NAME 39.Nm isdigit , 40.Nm isdigit_l 41.Nd decimal-digit single-byte character test 42.Sh SYNOPSIS 43.In ctype.h 44.Ft int 45.Fn isdigit "int c" 46.Ft int 47.Fn isdigit_l "int c" "locale_t locale" 48.Sh DESCRIPTION 49The 50.Fn isdigit 51and 52.Fn isdigit_l 53functions test for any decimal-digit character. 54In the C locale, the complete list of decimal digits is 0 and 1\(en9. 55.Ox 56always uses the C locale for these functions, 57ignoring the global locale, the thread-specific locale, and the 58.Fa locale 59argument. 60.Sh RETURN VALUES 61These functions return zero if the character tests false or 62non-zero if the character tests true. 63.Sh ENVIRONMENT 64On systems supporting non-ASCII single-byte character encodings, 65different 66.Fa c 67arguments may correspond to the digits, and the results of 68.Fn isdigit 69may depend on the 70.Ev LC_CTYPE 71.Xr locale 1 . 72.Sh SEE ALSO 73.Xr isalnum 3 , 74.Xr isalpha 3 , 75.Xr isascii 3 , 76.Xr isblank 3 , 77.Xr iscntrl 3 , 78.Xr isgraph 3 , 79.Xr islower 3 , 80.Xr isprint 3 , 81.Xr ispunct 3 , 82.Xr isspace 3 , 83.Xr isupper 3 , 84.Xr iswdigit 3 , 85.Xr isxdigit 3 , 86.Xr stdio 3 , 87.Xr toascii 3 , 88.Xr tolower 3 , 89.Xr toupper 3 , 90.Xr ascii 7 91.Sh STANDARDS 92The 93.Fn isdigit 94function conforms to 95.St -ansiC , 96and 97.Fn isdigit_l 98to 99.St -p1003.1-2008 . 100.Sh HISTORY 101The 102.Fn isdigit 103function first appeared in 104.At v7 , 105and 106.Fn isdigit_l 107has been available since 108.Ox 6.2 . 109.Sh CAVEATS 110The argument 111.Fa c 112must be 113.Dv EOF 114or representable as an 115.Vt unsigned char ; 116otherwise, the result is undefined. 117