Script for verifying the output of a FizzBuzz program. $ ./fizzbuzz.sh | ./fizzcheck.sh $ ./fizzcheck.sh ./fizzbuzz.sh`

fizzbuzz.sh

#!/bin/sh
# fizzbuzz.sh - A reference FizzBuzz program for testing fizzcheck.sh
# Author: Dustin King (cathodion@gmail.com)

limit=20
i=1

while expr $i '<=' $limit >/dev/null; do
	out=
	if expr $i % 3 = 0 >/dev/null; then out=Fizz; fi
	if expr $i % 5 = 0 >/dev/null; then out="$out"Buzz; fi
	if expr X$out = X'' >/dev/null; then out=$i; fi
	echo $out
	i=`expr $i + 1`
done

fizzcheck.sh

#!/bin/sh
# fizzcheck.sh - A script for verifying the output of FizzBuzz
# Author: Dustin King (cathodion@gmail.com)
# Original idea from https://twitter.com/qntm/status/329560932269301760

CMD=${1-'cat -'}

i=1
$CMD | while read actual; do
	expect=
	if expr $i % 3 = 0 >/dev/null; then expect=Fizz; fi
	if expr $i % 5 = 0 >/dev/null; then expect="$expect"Buzz; fi
	if expr X$expect = X'' >/dev/null; then expect=$i; fi
	
	if expr "X$actual" '!=' "X$expect" >/dev/null; then
		echo $i: Expected: \"$expect\", got \"$actual\"; 
		exit 1
	fi

	i=`expr $i + 1`
done