[0,2,3,4,5,7,8,9].combination(3){|x| puts x.join(" ") }
Standard input is empty
0 2 3 0 2 4 0 2 5 0 2 7 0 2 8 0 2 9 0 3 4 0 3 5 0 3 7 0 3 8 0 3 9 0 4 5 0 4 7 0 4 8 0 4 9 0 5 7 0 5 8 0 5 9 0 7 8 0 7 9 0 8 9 2 3 4 2 3 5 2 3 7 2 3 8 2 3 9 2 4 5 2 4 7 2 4 8 2 4 9 2 5 7 2 5 8 2 5 9 2 7 8 2 7 9 2 8 9 3 4 5 3 4 7 3 4 8 3 4 9 3 5 7 3 5 8 3 5 9 3 7 8 3 7 9 3 8 9 4 5 7 4 5 8 4 5 9 4 7 8 4 7 9 4 8 9 5 7 8 5 7 9 5 8 9 7 8 9