How to have sprintf to ignore trailing zeros

Question

I want to convert a number to a string with at most 15 digits to the right of the decimal point. By at most i mean that if last digits are

Answer 1

do you mean this ?

sprintf('%.15g', 3.0001001)
==> 3.0001001
sprintf('%.15g', 3.0001)
==> 3.0001