ecvt(3)ecvt(3)NAME
ecvt, ecvt_r, fcvt, fcvt_r, gcvt - Convert a floating-point number to a
string
SYNOPSIS
#include <stdlib.h>
char *ecvt(
double value,
int num_digits,
int *decimal_ptr,
int *sign ); char *fcvt(
double value,
int num_digits,
int *decimal_ptr,
int *sign ); char *gcvt(
double value,
int num_digits,
char *buffer );
The following obsolete functions are supported in order to maintain
backward compatibility with previous versions of the operating system.
You should not use them in new designs. int ecvt_r(
double value,
int num_digits,
int *decimal_ptr,
int *sign,
char *buffer,
int len ); int fcvt_r(
double value,
int num_digits,
int *decimal_ptr,
int *sign,
char *buffer,
int len );
LIBRARY
Standard C Library (libc)
PARAMETERS
Specifies the double value to be converted. Specifies the number of
digits in the resulting string. Holds the position of the decimal
point relative to the beginning of the string. A negative number means
the decimal point is to the left of the digits given in the string.
Holds a value of 0 (zero) if the value is positive or zero, and a
nonzero value if it is negative. Specifies the character array to be
used as scratch space in calculations and for storing the resulting
string. Specifies the length of buffer. Because ecvt temporarily
stores intermediate results of its calculations in the buffer, you must
specify a len greater than 370. A value of 400 is recommended.
DESCRIPTION
The ecvt(), fcvt(), and gcvt() functions convert floating-point numbers
to null-terminated strings.
The ecvt() function converts the value specified by the value parameter
to a null-terminated string of length num_digits, and returns a pointer
to it. The resulting low-order digit is rounded according to the cur‐
rent rounding mode. The decimal_ptr parameter is assigned to the posi‐
tion of the decimal point relative to the position of the string. The
sign parameter is assigned a value of 0 (zero) if value is positive or
zero, and a nonzero value if value is negative. The decimal point and
sign are not included in the string.
The fcvt() function is the same as the ecvt() function, except that it
rounds to the correct digit for outputting num_digits of digits in C or
FORTRAN F-format. In the F-format, num_digits is taken as the number of
digits desired after the decimal point.
The gcvt() function converts the value specified by the value parameter
to a null-terminated string, stores it in the array pointed to by the
buffer parameter, and then returns buffer. The gcvt() function attempts
to produce a string of num_digits significant digits in FORTRAN F-for‐
mat. If this is not possible, then E-format is used. The string is
ready for printing, complete with minus sign, decimal point, or expo‐
nent, as appropriate. Trailing zeros are suppressed.
In the F-format, num_digits is the number of digits desired after the
decimal point. Very large numbers produce a very long string of digits
before the decimal point, and then num_digits of digits after the deci‐
mal point. For large numbers, it is preferable to use the gcvt() or
ecvt() function so that the E-format will be used.
The ecvt(), fcvt(), and gcvt() functions represent the following spe‐
cial values that are specified in IEEE Standard 754-1985 for floating-
point arithmetic according to the following table.
ecvt(3)