NAME
	luhncheck - Check number with Luhn's algorithm

SYNOPSIS
	luhncheck number ...

DESCRIPTION
	The luhncheck utility checks that a number, containing a
	check digit, is valid according to Luhn's algorithm.

OPTIONS
	The luhncheck utility conforms to the Base Definitions volume
	of POSIX.1-2017, Section 12.2, Utility Syntax Guidelines.

	No options are supported.

OPERANDS
	The following operand is supported:

	number
		Number to check.

STDOUT
	The luhncheck utility will print one line per number, in the
	order they are provided in the command line, to the standard
	output. Each line will be use the format

		"%s is %s\n", number, <"OK" if valid, "invalid" otherwise>.

EXIT STATUS
	The following exit values are returned:

	0	All numbers are valid.

	1	At least one number is invalid.

	2	An error occured.

SEE ALSO
	gluhncheck(1)