ecvt, fcvt - convert a floating-point number to a string


#include <stdlib.h>

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)):

ecvt(), fcvt(): _SVID_SOURCE || _XOPEN_SOURCE >= 500


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 non-zero, 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, 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 specifies 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().


SVr2; marked as LEGACY in POSIX.1-2001. POSIX.1-2008 removes the specifications 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").


ecvt_r(3), gcvt(3), qecvt(3), setlocale(3), sprintf(3)


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