ecvt(3) — Linux manual page


ecvt(3)                 Library Functions Manual                 ecvt(3)

NAME         top

       ecvt, fcvt - convert a floating-point number to a string

LIBRARY         top

       Standard C library (libc, -lc)

SYNOPSIS         top

       #include <stdlib.h>

       [[deprecated]] char *ecvt(double number, int ndigits,
                                 int *restrict decpt, int *restrict sign);
       [[deprecated]] char *fcvt(double number, int ndigits,
                                 int *restrict decpt, int *restrict sign);

   Feature Test Macro Requirements for glibc (see

       ecvt(), fcvt():
           Since glibc 2.17
               (_XOPEN_SOURCE >= 500 && ! (_POSIX_C_SOURCE >= 200809L))
                   || /* glibc >= 2.20 */ _DEFAULT_SOURCE
                   || /* glibc <= 2.19 */ _SVID_SOURCE
           glibc 2.12 to glibc 2.16:
               (_XOPEN_SOURCE >= 500 && ! (_POSIX_C_SOURCE >= 200112L))
                   || _SVID_SOURCE
           Before glibc 2.12:
               _SVID_SOURCE || _XOPEN_SOURCE >= 500

DESCRIPTION         top

       The ecvt() function converts number to a null-terminated string
       of ndigits digits (where ndigits is reduced to a system-specific
       limit determined by the precision of a double), and returns a
       pointer to the string.  The high-order digit is nonzero, unless
       number is zero.  The low order digit is rounded.  The string
       itself does not contain a decimal point; however, the position of
       the decimal point relative to the start of the string is stored
       in *decpt.  A negative value for *decpt means that the decimal
       point is to the left of the start of the string.  If the sign of
       number is negative, *sign is set to a nonzero value, otherwise it
       is set to 0.  If number is zero, it is unspecified whether *decpt
       is 0 or 1.

       The fcvt() function is identical to ecvt(), except that ndigits
       specifies the number of digits after the decimal point.

RETURN VALUE         top

       Both the ecvt() and fcvt() functions return a pointer to a static
       string containing the ASCII representation of number.  The static
       string is overwritten by each call to ecvt() or fcvt().

ATTRIBUTES         top

       For an explanation of the terms used in this section, see
       │ Interface               Attribute     Value               │
       │ ecvt()                  │ Thread safety │ MT-Unsafe race:ecvt │
       │ fcvt()                  │ Thread safety │ MT-Unsafe race:fcvt │

STANDARDS         top


HISTORY         top

       SVr2; marked as LEGACY in POSIX.1-2001.  POSIX.1-2008 removes the
       specifications of ecvt() and fcvt(), recommending the use of
       sprintf(3) instead (though snprintf(3) may be preferable).

NOTES         top

       Not all locales use a point as the radix character ("decimal

SEE ALSO         top

       ecvt_r(3), gcvt(3), qecvt(3), setlocale(3), sprintf(3)

COLOPHON         top

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Linux man-pages 6.9.1          2024-05-02                        ecvt(3)

Pages that refer to this page: ecvt_r(3)gcvt(3)qecvt(3)