Printf width specifier to maintain precision of floating-point value

Question

Is there a printf width specifier which can be applied to a floating point specifier that would automatically format the output to the necessary number of s

Answer 1

If you are only interested in the bit (resp hex pattern) you could use the %a format. This guarantees you:

The default precision suffices for an exact representation of the value if an exact representation in base 2 exists and otherwise is sufficiently large to distinguish values of type double.

I'd have to add that this is only available since C99.