Equivalent of C++ std::setprecision(20) using printf in C

Question

I want to print doubles in decimal notation with full precision (but without extra zeros at the end of the number). In C++ I can use:

std::setprecision(20);
cout << d; // Here d is a double

What would be the equivalent C code using printf?

Answer 1

You can use the "%.20g" specifier. g is IMHO usually better than f since it doesn't print trailing zeros, and handles large/small values sensibly (changing to e format).

Also note that with the "g" specifier, the precision (the "20" in this case) specifies the number of significant digits rather than the number of digits after the decimal point.