[0,1,2,3,5,6,7,8].combination(4){|x| puts x.join(" ") }
Standard input is empty
0 1 2 3 0 1 2 5 0 1 2 6 0 1 2 7 0 1 2 8 0 1 3 5 0 1 3 6 0 1 3 7 0 1 3 8 0 1 5 6 0 1 5 7 0 1 5 8 0 1 6 7 0 1 6 8 0 1 7 8 0 2 3 5 0 2 3 6 0 2 3 7 0 2 3 8 0 2 5 6 0 2 5 7 0 2 5 8 0 2 6 7 0 2 6 8 0 2 7 8 0 3 5 6 0 3 5 7 0 3 5 8 0 3 6 7 0 3 6 8 0 3 7 8 0 5 6 7 0 5 6 8 0 5 7 8 0 6 7 8 1 2 3 5 1 2 3 6 1 2 3 7 1 2 3 8 1 2 5 6 1 2 5 7 1 2 5 8 1 2 6 7 1 2 6 8 1 2 7 8 1 3 5 6 1 3 5 7 1 3 5 8 1 3 6 7 1 3 6 8 1 3 7 8 1 5 6 7 1 5 6 8 1 5 7 8 1 6 7 8 2 3 5 6 2 3 5 7 2 3 5 8 2 3 6 7 2 3 6 8 2 3 7 8 2 5 6 7 2 5 6 8 2 5 7 8 2 6 7 8 3 5 6 7 3 5 6 8 3 5 7 8 3 6 7 8 5 6 7 8