Tribblix: 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