How to create tab space using @sprintf?

General Usage
2

Why writing to an array of strings? You can write directly to the file:

julia> open("test.txt", "w") do io
           for i in 1:5
               @printf(io, "\t o%-6d  I : %9.6f, %9.6f\n", i, rand(), -rand())
           end
       end

shell> cat test.txt
         o1       I :  0.499033, -0.518227
         o2       I :  0.452359, -0.057112
         o3       I :  0.137529, -0.954224
         o4       I :  0.792647, -0.996261
         o5       I :  0.859669, -0.768580