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ISDIGIT(3)		    Library Functions Manual		    ISDIGIT(3)

NAME
       isdigit,	 isnumber,  isdigit_l,	isnumber_l  -- decimal-digit character
       test

LIBRARY
       Standard	C Library (libc, -lc)

SYNOPSIS
       #include	<ctype.h>

       int
       isdigit(int c);

       int
       isnumber(int c);

       int
       isdigit_l(int c,	locale_t loc);

       int
       isnumber_l(int c, locale_t loc);

DESCRIPTION
       The isdigit() and isdigit_l() functions test for	a decimal digit	 char-
       acter.	Regardless  of	locale,	this includes the following characters
       only:

       ``0''								       ``1''``2''``3''``4''
       ``5''								       ``6''``7''``8''``9''

       The isnumber() and isnumber_l() functions behave	similarly to isdigit()
       and isdigit_l(),	but may	recognize additional characters, depending  on
       the current locale setting.

       The  value of the argument must be representable	as an unsigned char or
       the value of EOF.

       The _l-suffixed versions	take an	explicit locale	argument, whereas  the
       non-suffixed versions use the current global or per-thread locale.

RETURN VALUES
       The  isdigit(), isdigit_l(), isnumber(),	and isnumber_l() functions re-
       turn zero if the	character tests	false and return non-zero if the char-
       acter tests true.

COMPATIBILITY
       The 4.4BSD extension of accepting arguments outside of the range	of the
       unsigned	char type in locales with large	character sets	is  considered
       obsolete	 and  may not be supported in future releases.	The iswdigit()
       or iswdigit_l() function	should be used instead.

SEE ALSO
       ctype(3),   ctype_l(3),	 iswdigit(3),	iswdigit_l(3),	 multibyte(3),
       xlocale(3), ascii(7)

STANDARDS
       The  isdigit() function conforms	to ISO/IEC 9899:1990 ("ISO C90").  The
       isdigit_l() function conforms to	IEEE Std 1003.1-2008 ("POSIX.1").

HISTORY
       The isnumber() function appeared	in 4.4BSD.

FreeBSD	14.3		       December	19, 2022		    ISDIGIT(3)

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<https://man.freebsd.org/cgi/man.cgi?query=isnumber&sektion=3&manpath=FreeBSD+14.3-RELEASE+and+Ports>

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