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ECVT(3P)                   POSIX Programmer's Manual                  ECVT(3P)



PROLOG
       This manual page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may dif-
       fer (consult the corresponding Linux manual page for details of Linux behavior), or the interface  may  not  be
       implemented on Linux.

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 implementa-
       tion-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 unspec-
       ified.

       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 spec-
       ification format of printf()) in the array pointed to by buf and shall return buf. It shall produce ndigit sig-
       nificant  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 set-
       locale() 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, Stan-
       dard  for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifica-
       tions 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 Stan-
       dard, 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 .



IEEE/The Open Group                  2003                             ECVT(3P)