| ECVT(3) | Library Functions Manual | ECVT(3) |
ecvt, fcvt,
gcvt — convert double to
ASCII string
#include
<stdlib.h>
char *
ecvt(double
value, int ndigit,
int * restrict decpt,
int * restrict sign);
char *
fcvt(double
value, int ndigit,
int * restrict decpt,
int * restrict sign);
char *
gcvt(double
value, int ndigit,
char *buf);
The
ecvt(),
fcvt() and gcvt() functions
convert the double precision floating-point number
value to a NUL-terminated ASCII string.
The
ecvt()
function converts value to a NUL-terminated string of
exactly ndigit digits and returns a pointer to that
string. The result is padded with zeroes from left to right as needed. There
are no leading zeroes unless value itself is 0. The
least significant digit is rounded in an implementation-dependent manner.
The position of the decimal point relative to the beginning of the string is
stored in decpt. A negative value indicates that the
decimal point is located to the left of the returned digits (this occurs
when there is no whole number component to value). If
value is zero, it is unspecified whether the integer
pointed to by decpt will be 0 or 1. The decimal point
itself is not included in the returned string. If the sign of the result is
negative, the integer pointed to by sign is non-zero;
otherwise, it is 0.
If the converted value is out of range or is not representable, the contents of the returned string are unspecified.
The
fcvt()
function is identical to ecvt() with the exception
that ndigit specifies the number of digits after the
decimal point (zero-padded as needed).
The
gcvt()
function converts value to a NUL-terminated string
similar to the %g printf(3) format
specifier and stores the result in buf. It produces
ndigit significant digits similar to the %f
printf(3) format specifier where
possible. If ndigit does allow sufficient precision,
the result is stored in exponential notation similar to the %e
printf(3) format specifier. If
value is less than zero, buf
will be prefixed with a minus sign. A decimal point is included in the
returned string if value is not a whole number. Unlike
the ecvt() and fcvt()
functions, buf is not zero-padded.
The ecvt(), fcvt()
and gcvt() functions return a NUL-terminated string
representation of value.
The ecvt() and
fcvt() functions return a pointer to internal
storage space that will be overwritten by subsequent calls to either
function.
The maximum possible precision of the return value is limited by the precision of a double and may not be the same on all architectures.
The snprintf(3) function is preferred over these functions for new code.
The ecvt(), fcvt()
and gcvt() functions conform to
IEEE Std 1003.1-2001 (“POSIX.1”).
| May 31, 2007 | macOS 15.0 |