ECVT(3) Linux Programmer's Manual ECVT(3)
ecvt, fcvt - convert a floating-point number to a string.
char *ecvt(double number, int ndigits, int *decpt, int *sign);
char *fcvt(double number, int ndigits, int *decpt, int *sign);
The ecvt() function converts number to a null-terminated string of
ndigits digits (where ndigits is reduced to an system-specific limit
determined by the precision of a double), and returns a pointer to the
string. The high-order digit is nonzero, unless number is zero. The low
order digit is rounded. The string itself does not contain a decimal
point; however, the position of the decimal point relative to the start
of the string is stored in *decpt. A negative value for *decpt means
that the decimal point is to the left of the start of the string. If
the sign of number is negative, *sign is set to a non-zero value, oth-
erwise it's set to 0. If number is zero, it is unspecified whether
*decpt is 0 or 1.
The fcvt() function is identical to ecvt(), except that ndigits speci-
fies the number of digits after the decimal point.
Both the ecvt() and fcvt() functions return a pointer to a static
string containing the ASCII representation of number. The static
string is overwritten by each call to ecvt() or fcvt().
These functions are obsolete. Instead, sprintf() is recommended. Linux
libc4 and libc5 specified the type of ndigits as size_t. Not all
locales use a point as the radix character (`decimal point').
ecvt_r(3), gcvt(3), qecvt(3), setlocale(3), sprintf(3)