adime_double2string (3) - Linux Man Pages
DESCRIPTIONFunction for pretty-printing floating point numbers: The number gets at most 10 digits to the left of the decimal point, at most 9 to the right of it, and at most 10 totally. If the absolute value of the number is >= 10000000000 or < 0.000001, it is written in exponential form instead. Exponential form has at most 6 digits in the mantissa, so that the total number of digits never exceeds 9. Does not support Unicode.