isdigit,
isdigit_l —
decimal-digit single-byte character test
#include
<ctype.h>
int
isdigit(
int
c);
int
isdigit_l(
int
c,
locale_t
locale);
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.
These functions return zero if the character tests false or non-zero if the
character tests true.
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).
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)
The
isdigit() function conforms to
ANSI X3.159-1989
(“ANSI C89”), and
isdigit_l() to
IEEE Std 1003.1-2008
(“POSIX.1”).
The
isdigit() function first appeared in
Version 7 AT&T UNIX, and
isdigit_l() has been available since
OpenBSD 6.2.
The argument
c must be
EOF or representable as an
unsigned char; otherwise, the result is
undefined.
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