NAME
isdigit
, isdigit_l
— decimal-digit single-byte
character test
SYNOPSIS
#include
<ctype.h>
int
isdigit
(int
c);
int
isdigit_l
(int
c, locale_t
locale);
DESCRIPTION
The
isdigit
()
and
isdigit_l
()
functions test for any decimal-digit character. The complete list of decimal
digits is 0 and 1–9, in any locale.
RETURN VALUES
These functions return zero if the character tests false or non-zero if the character tests true.
ENVIRONMENT
On systems supporting non-ASCII single-byte character encodings,
different c arguments may correspond to the digits,
and the results of isdigit
() may depend on the
LC_CTYPE
locale(1).
SEE ALSO
isalnum(3), isalpha(3), isascii(3), isblank(3), iscntrl(3), isgraph(3), islower(3), isprint(3), ispunct(3), isspace(3), isupper(3), iswdigit(3), isxdigit(3), stdio(3), toascii(3), tolower(3), toupper(3), ascii(7)
STANDARDS
The isdigit
() function conforms to
ANSI X3.159-1989 (“ANSI C89”),
and isdigit_l
() to IEEE Std
1003.1-2008 (“POSIX.1”).
HISTORY
The isdigit
() function first appeared in
Version 7 AT&T UNIX, and
isdigit_l
() has been available since
OpenBSD 6.2.
CAVEATS
The argument c must be
EOF
or representable as an unsigned
char; otherwise, the result is undefined.