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ECVT(3)                  BSD Library Functions Manual                  ECVT(3)

NAME
     ecvt, fcvt, gcvt -- convert double to ASCII 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
     These functions are provided for compatibility with legacy code.  New code should use the snprintf(3)
     function for improved safety and portability.

     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 implementationdependent
     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 unspec-ified unspecified
     ified 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; nonzero;
     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 dig-its digits
     its 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 speci-fier specifier
     fier 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.

RETURN VALUES
     The ecvt(), fcvt() and gcvt() functions return a NUL-terminated string representation of value.

WARNINGS
     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.

SEE ALSO
     printf(3), strtod(3)

STANDARDS
     The ecvt(), fcvt() and gcvt() functions conform to IEEE Std 1003.1-2001 (``POSIX.1'').

BSD                            October 11, 2013                            BSD