illumos: manual page: ecvt.3c

ECVT(3C) Standard C Library Functions ECVT(3C)

NAME

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

SYNOPSIS

#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);

DESCRIPTION

The ecvt(), fcvt() and gcvt() functions convert floating-point numbers to
null-terminated strings.

ecvt()
The ecvt() function converts value to a null-terminated string of ndigit
digits (where ndigit is reduced to an unspecified limit determined by the
precision of a double) and returns a pointer to the string. The high-
order digit is non-zero, unless the value is 0. The low-order digit is
rounded. The position of the radix character relative to the beginning
of the string is stored in the integer pointed to by decpt (negative
means to the left of the returned digits). The radix character 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.

fcvt()
The fcvt() function is identical to ecvt() except that ndigit specifies
the number of digits desired after the radix point. The total number of
digits in the result string is restricted to an unspecified limit as
determined by the precision of a double.

gcvt()
The gcvt() function converts value to a null-terminated string (similar
to that of the %g format of printf(3C)) in the array pointed to by buf
and returns buf. It produces ndigit significant digits (limited to an
unspecified value determined by the precision of a double) in %f if
possible, or %e (scientific notation) otherwise. A minus sign is
included in the returned string if value is less than 0. A radix
character is included in the returned string if value is not a whole
number. Trailing zeros are suppressed where value is not a whole number.
The radix character is determined by the current locale. If setlocale(3C)
has not been called successfully, the default locale, POSIX, is used.
The default locale specifies a period (.) as the radix character. The
LC_NUMERIC category determines the value of the radix character within
the current locale.

RETURN VALUES

The ecvt() and fcvt() functions return a pointer to a null-terminated
string of digits.

The gcvt() function returns buf.

ERRORS

No errors are defined.

USAGE

The return values from ecvt() and fcvt() might point to thread-specific
data that can be overwritten by subsequent calls to these functions by
the same thread.

For portability to implementations conforming to earlier versions of
Solaris, sprintf(3C) is preferred over this function.

ATTRIBUTES