1ECVT(P) POSIX Programmer's Manual ECVT(P)
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6 ecvt, fcvt, gcvt - convert a floating-point number to a string (LEGACY)
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9 #include <stdlib.h>
10 char *ecvt(double value, int ndigit, int *restrict decpt,
12 int *restrict sign);
13 char *fcvt(double value, int ndigit, int *restrict decpt,
14 int *restrict sign);
15 char *gcvt(double value, int ndigit, char *buf);
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19 The ecvt(), fcvt(), and gcvt() functions shall convert floating-point
20 numbers to null-terminated strings.
21 The ecvt() function shall convert value to a null-terminated string of
23 ndigit digits (where ndigit is reduced to an unspecified limit deter‐
24 mined by the precision of a double) and return a pointer to the string.
25 The high-order digit shall be non-zero, unless the value is 0. The low-
26 order digit shall be rounded in an implementation-defined manner. The
27 position of the radix character relative to the beginning of the string
28 shall be stored in the integer pointed to by decpt (negative means to
29 the left of the returned digits). If value is zero, it is unspecified
30 whether the integer pointed to by decpt would be 0 or 1. The radix
31 character shall not be included in the returned string. If the sign of
32 the result is negative, the integer pointed to by sign shall be non-
33 zero; otherwise, it shall be 0.
34 If the converted value is out of range or is not representable, the
36 contents of the returned string are unspecified.
37 The fcvt() function shall be equivalent to ecvt(), except that ndigit
39 specifies the number of digits desired after the radix character. The
40 total number of digits in the result string is restricted to an unspec‐
41 ified limit as determined by the precision of a double.
42 The gcvt() function shall convert value to a null-terminated string
44 (similar to that of the %g conversion specification format of printf())
45 in the array pointed to by buf and shall return buf. It shall produce
46 ndigit significant digits (limited to an unspecified value determined
47 by the precision of a double) in the %f conversion specification format
48 of printf() if possible, or the %e conversion specification format of
49 printf() (scientific notation) otherwise. A minus sign shall be
50 included in the returned string if value is less than 0. A radix char‐
51 acter shall be included in the returned string if value is not a whole
52 number. Trailing zeros shall be suppressed where value is not a whole
53 number. The radix character is determined by the current locale. If
54 setlocale() has not been called successfully, the default locale,
55 POSIX, is used. The default locale specifies a period ( '.' ) as the
56 radix character. The LC_NUMERIC category determines the value of the
57 radix character within the current locale.
58 These functions need not be reentrant. A function that is not required
60 to be reentrant is not required to be thread-safe.
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63 The ecvt() and fcvt() functions shall return a pointer to a null-termi‐
64 nated string of digits.
65 The gcvt() function shall return buf.
67 The return values from ecvt() and fcvt() may point to static data which
69 may be overwritten by subsequent calls to these functions.
70
72 No errors are defined.
73 The following sections are informative.
75
77 None.
78
80 The sprintf() function is preferred over this function.
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83 None.
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86 These functions may be withdrawn in a future version.
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89 printf() , setlocale() , the Base Definitions volume of
90 IEEE Std 1003.1-2001, <stdlib.h>
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93 Portions of this text are reprinted and reproduced in electronic form
94 from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
95 -- Portable Operating System Interface (POSIX), The Open Group Base
96 Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
97 Electrical and Electronics Engineers, Inc and The Open Group. In the
98 event of any discrepancy between this version and the original IEEE and
99 The Open Group Standard, the original IEEE and The Open Group Standard
100 is the referee document. The original Standard can be obtained online
101 at http://www.opengroup.org/unix/online.html .
102IEEE/The Open Group 2003 ECVT(P)