ecvt(3) - f37

1ECVT(3)                    Linux Programmer's Manual                   ECVT(3)
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NAME

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

9       #include <stdlib.h>
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11       char *ecvt(double number, int ndigits, int *restrict decpt,
12                  int *restrict sign);
13       char *fcvt(double number, int ndigits, int *restrict decpt,
14                  int *restrict sign);
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16   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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18       ecvt(), fcvt():
19           Since glibc 2.17
20               (_XOPEN_SOURCE >= 500 && ! (_POSIX_C_SOURCE >= 200809L))
21                   || /* Glibc >= 2.20 */ _DEFAULT_SOURCE
22                   || /* Glibc <= 2.19 */ _SVID_SOURCE
23           Glibc versions 2.12 to 2.16:
24               (_XOPEN_SOURCE >= 500 && ! (_POSIX_C_SOURCE >= 200112L))
25                   || _SVID_SOURCE
26           Before glibc 2.12:
27               _SVID_SOURCE || _XOPEN_SOURCE >= 500
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DESCRIPTION

30       The  ecvt()  function  converts  number  to a null-terminated string of
31       ndigits digits (where ndigits is reduced to a system-specific limit de‐
32       termined  by  the  precision of a double), and returns a pointer to the
33       string.  The high-order digit is nonzero, unless number is  zero.   The
34       low order digit is rounded.  The string itself does not contain a deci‐
35       mal point; however, the position of the decimal point relative  to  the
36       start  of  the string is stored in *decpt.  A negative value for *decpt
37       means that the decimal point is to the left of the start of the string.
38       If  the  sign  of  number is negative, *sign is set to a nonzero value,
39       otherwise it is set to 0.  If number is zero, it is unspecified whether
40       *decpt is 0 or 1.
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42       The  fcvt() function is identical to ecvt(), except that ndigits speci‐
43       fies the number of digits after the decimal point.
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RETURN VALUE

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

51       For an  explanation  of  the  terms  used  in  this  section,  see  at‐
52       tributes(7).
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54       ┌────────────────────────────────┬───────────────┬─────────────────────┐
55       │Interface                       │ Attribute     │ Value               │
56       ├────────────────────────────────┼───────────────┼─────────────────────┤
57       │ecvt()                          │ Thread safety │ MT-Unsafe race:ecvt │
58       ├────────────────────────────────┼───────────────┼─────────────────────┤
59       │fcvt()                          │ Thread safety │ MT-Unsafe race:fcvt │
60       └────────────────────────────────┴───────────────┴─────────────────────┘
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CONFORMING TO

63       SVr2; marked as LEGACY in POSIX.1-2001.  POSIX.1-2008 removes the spec‐
64       ifications of ecvt() and fcvt(), recommending the use of sprintf(3) in‐
65       stead (though snprintf(3) may be preferable).
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NOTES

68       Not all locales use a point as the radix character ("decimal point").
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COLOPHON

74       This  page  is  part of release 5.13 of the Linux man-pages project.  A
75       description of the project, information about reporting bugs,  and  the
76       latest     version     of     this    page,    can    be    found    at
77       https://www.kernel.org/doc/man-pages/.
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81                                  2021-03-22                           ECVT(3)