ISDIGIT(3)

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. In the C locale, the complete list of decimal digits is 0 and 1–9. OpenBSD always uses the C locale for these functions, ignoring the global locale, the thread-specific locale, and the locale argument.

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 ansiC, and isdigit_l() to p1003.1-2008.

HISTORY
The isdigit() function first appeared in 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.