.\"	$OpenBSD: isdigit.3,v 1.12 2017/09/05 03:16:13 schwarze Exp $
.\"
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.\" Copyright (c) 2017 Ingo Schwarze <schwarze@openbsd.org>
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.\" the American National Standards Committee X3, on Information
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.Dd $Mdocdate: September 5 2017 $
.Dt ISDIGIT 3
.Os
.Sh NAME
.Nm isdigit ,
.Nm isdigit_l
.Nd decimal-digit single-byte character test
.Sh SYNOPSIS
.In ctype.h
.Ft int
.Fn isdigit "int c"
.Ft int
.Fn isdigit_l "int c" "locale_t locale"
.Sh DESCRIPTION
The
.Fn isdigit
and
.Fn isdigit_l
functions test for any decimal-digit character.
The complete list of decimal digits is 0 and 1\(en9, in any locale.
.Sh RETURN VALUES
These functions return zero if the character tests false or
non-zero if the character tests true.
.Sh ENVIRONMENT
On systems supporting non-ASCII single-byte character encodings,
different
.Fa c
arguments may correspond to the digits, and the results of
.Fn isdigit
may depend on the
.Ev LC_CTYPE
.Xr locale 1 .
.Sh SEE ALSO
.Xr isalnum 3 ,
.Xr isalpha 3 ,
.Xr isascii 3 ,
.Xr isblank 3 ,
.Xr iscntrl 3 ,
.Xr isgraph 3 ,
.Xr islower 3 ,
.Xr isprint 3 ,
.Xr ispunct 3 ,
.Xr isspace 3 ,
.Xr isupper 3 ,
.Xr iswdigit 3 ,
.Xr isxdigit 3 ,
.Xr stdio 3 ,
.Xr toascii 3 ,
.Xr tolower 3 ,
.Xr toupper 3 ,
.Xr ascii 7
.Sh STANDARDS
The
.Fn isdigit
function conforms to
.St -ansiC ,
and
.Fn isdigit_l
to
.St -p1003.1-2008 .
.Sh HISTORY
The
.Fn isdigit
function first appeared in
.At v7 ,
and
.Fn isdigit_l
has been available since
.Ox 6.2 .
.Sh CAVEATS
The argument
.Fa c
must be
.Dv EOF
or representable as an
.Li unsigned char ;
otherwise, the result is undefined.