1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
|
'\" t
.\" Copyright, the authors of the Linux man-pages project
.\"
.\" SPDX-License-Identifier: Linux-man-pages-copyleft
.\"
.TH ecvt 3 2025-05-17 "Linux man-pages (unreleased)"
.SH NAME
ecvt, fcvt \- convert a floating-point number to a string
.SH LIBRARY
Standard C library
.RI ( libc ,\~ \-lc )
.SH SYNOPSIS
.nf
.B #include <stdlib.h>
.P
.BI "[[deprecated]] char *ecvt(double " number ", int " ndigits ,
.BI " int *restrict " decpt ", int *restrict " sign );
.BI "[[deprecated]] char *fcvt(double " number ", int " ndigits ,
.BI " int *restrict " decpt ", int *restrict " sign );
.fi
.P
.RS -4
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.RE
.P
.BR ecvt (),
.BR fcvt ():
.nf
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
.\" || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED
.fi
.SH DESCRIPTION
The
.BR ecvt ()
function converts
.I number
to a null-terminated
string of
.I ndigits
digits (where
.I ndigits
is reduced to a
system-specific limit determined by the precision of a
.IR double ),
and returns a pointer to the string.
The high-order digit is nonzero, unless
.I 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
.IR *decpt .
A negative value for
.I *decpt
means that
the decimal point is to the left of the start of the string.
If the sign of
.I number
is negative,
.I *sign
is set to a nonzero value,
otherwise it is set to 0.
If
.I number
is zero, it is unspecified whether
.I *decpt
is 0 or 1.
.P
The
.BR fcvt ()
function is identical to
.BR ecvt (),
except that
.I ndigits
specifies the number of digits after the decimal point.
.SH RETURN VALUE
Both the
.BR ecvt ()
and
.BR fcvt ()
functions return a pointer to a
static string containing the ASCII representation of
.IR number .
The static string is overwritten by each call to
.BR ecvt ()
or
.BR fcvt ().
.SH ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.TS
allbox;
lbx lb lb
l l l.
Interface Attribute Value
T{
.na
.nh
.BR ecvt ()
T} Thread safety MT-Unsafe race:ecvt
T{
.na
.nh
.BR fcvt ()
T} Thread safety MT-Unsafe race:fcvt
.TE
.SH STANDARDS
None.
.SH HISTORY
SVr2;
marked as LEGACY in POSIX.1-2001.
POSIX.1-2008 removes the specifications of
.BR ecvt ()
and
.BR fcvt (),
recommending the use of
.BR sprintf (3)
instead (though
.BR snprintf (3)
may be preferable).
.SH NOTES
.\" Linux libc4 and libc5 specified the type of
.\" .I ndigits
.\" as
.\" .IR size_t .
Not all locales use a point as the radix character ("decimal point").
.SH SEE ALSO
.BR ecvt_r (3),
.BR gcvt (3),
.BR qecvt (3),
.BR setlocale (3),
.BR sprintf (3)
|
