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NAME
ecvt, fcvt, gcvt - convert a floating-point number to a string (LEGACY)
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 shall convert floating-point numbers to null-terminated strings.
The ecvt() function shall convert 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 return a pointer to the
string. The high-order digit shall be non-zero, unless the value is 0. The low-order digit shall be
rounded in an implementation-defined manner. The position of the radix character relative to the
beginning of the string shall be stored in the integer pointed to by decpt (negative means to the left of
the returned digits). If value is zero, it is unspecified whether the integer pointed to by decpt would
be 0 or 1. The radix character shall not be included in the returned string. If the sign of the result is
negative, the integer pointed to by sign shall be non-zero; otherwise, it shall be 0.
If the converted value is out of range or is not representable, the contents of the returned string are
unspecified.
The fcvt() function shall be equivalent to ecvt(), except that ndigit specifies the number of digits
desired after the radix character. The total number of digits in the result string is restricted to an
unspecified limit as determined by the precision of a double.
The gcvt() function shall convert value to a null-terminated string (similar to that of the %g conversion
specification format of printf()) in the array pointed to by buf and shall return buf. It shall produce
ndigit significant digits (limited to an unspecified value determined by the precision of a double) in
the %f conversion specification format of printf() if possible, or the %e conversion specification format
of printf() (scientific notation) otherwise. A minus sign shall be included in the returned string if
value is less than 0. A radix character shall be included in the returned string if value is not a whole
number. Trailing zeros shall be suppressed where value is not a whole number. The radix character is
determined by the current locale. If setlocale() 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.
These functions need not be reentrant. A function that is not required to be reentrant is not required to
be thread-safe.
RETURN VALUE
The ecvt() and fcvt() functions shall return a pointer to a null-terminated string of digits.
The gcvt() function shall return buf.
The return values from ecvt() and fcvt() may point to static data which may be overwritten by subsequent
calls to these functions.
ERRORS
No errors are defined.
The following sections are informative.
EXAMPLES
None.
APPLICATION USAGE
The sprintf() function is preferred over this function.
RATIONALE
None.
FUTURE DIRECTIONS
These functions may be withdrawn in a future version.
SEE ALSO
printf() , setlocale() , the Base Definitions volume of IEEE Std 1003.1-2001, <stdlib.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition,
Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers,
Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The
original Standard can be obtained online at http://www.opengroup.org/unix/online.html .