char *ecvt(double number, int ndigits, int *decpt, int *sign);
char *fcvt(double number, int ndigits, int *decpt, int *sign);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
Since glibc 2.12:
(_XOPEN_SOURCE >= 500 ||
_XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED) &&
!(_POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE >= 600)
Before glibc 2.12:
_SVID_SOURCE || _XOPEN_SOURCE >= 500 ||
_XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED
The ecvt() function converts number to a null-terminated string of
ndigits digits (where ndigits is reduced to a 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 deci-
mal 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 nonzero value,
otherwise it is 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().
Multithreading (see pthreads(7))
The ecvt() and fcvt() functions are not thread-safe.
SVr2; marked as LEGACY in POSIX.1-2001. POSIX.1-2008 removes the spec-
ifications of ecvt() and fcvt(), recommending the use of sprintf(3)
instead (though snprintf(3) may be preferable).
Linux libc4 and libc5 specified the type of ndigits as size_t. Not all
locales use a point as the radix character ("decimal point").
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