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1.\" Copyright (c) 1990, 1991 The Regents of the University of California.
2.\" All rights reserved.
3.\"
4.\" This code is derived from software contributed to Berkeley by
5.\" the American National Standards Committee X3, on Information
6.\" Processing Systems.
7.\"
8.\" Redistribution and use in source and binary forms, with or without
9.\" modification, are permitted provided that the following conditions
10.\" are met:
11.\" 1. Redistributions of source code must retain the above copyright
12.\" notice, this list of conditions and the following disclaimer.
13.\" 2. Redistributions in binary form must reproduce the above copyright
14.\" notice, this list of conditions and the following disclaimer in the
15.\" documentation and/or other materials provided with the distribution.
16.\" 3. Neither the name of the University nor the names of its contributors
17.\" may be used to endorse or promote products derived from this software
18.\" without specific prior written permission.
19.\"
20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30.\" SUCH DAMAGE.
31.\"
32.\" $OpenBSD: strtod.3,v 1.8 2003/06/02 20:18:38 millert Exp $
33.\"
34.Dd June 29, 1991
35.Dt STRTOD 3
36.Os
37.Sh NAME
38.Nm strtod
39.Nd convert
40.Tn ASCII
41string to double
42.Sh SYNOPSIS
43.Fd #include <stdlib.h>
44.Ft double
45.Fn strtod "const char *nptr" "char **endptr"
46.Sh DESCRIPTION
47The
48.Fn strtod
49function converts the initial portion of the string pointed to by
50.Fa nptr
51to
52.Li double
53representation.
54.Pp
55The expected form of the string is an optional plus
56.Pq Ql +
57or minus sign
58.Pq Ql -
59followed by a sequence of digits optionally containing
60a decimal-point character, optionally followed by an exponent.
61An exponent consists of an
62.Sq E
63or
64.Sq e ,
65followed by an optional plus or minus sign, followed by a sequence of digits.
66.Pp
67Leading whitespace characters in the string (as defined by the
68.Xr isspace 3
69function) are skipped.
70.Sh RETURN VALUES
71The
72.Fn strtod
73function returns the converted value, if any.
74.Pp
75If
76.Fa endptr
77is not
78.Dv NULL ,
79a pointer to the character after the last character used
80in the conversion is stored in the location referenced by
81.Fa endptr .
82.Pp
83If no conversion is performed, zero is returned and the value of
84.Fa nptr
85is stored in the location referenced by
86.Fa endptr .
87.Pp
88If the correct value would cause overflow, plus or minus
89.Dv HUGE_VAL
90is returned (according to the sign of the value), and
91.Er ERANGE
92is stored in
93.Va errno .
94If the correct value would cause underflow, zero is returned and
95.Er ERANGE
96is stored in
97.Va errno .
98.Sh ERRORS
99.Bl -tag -width Er
100.It Bq Er ERANGE
101Overflow or underflow occurred.
102.El
103.Sh SEE ALSO
104.Xr atof 3 ,
105.Xr atoi 3 ,
106.Xr atol 3 ,
107.Xr strtol 3 ,
108.Xr strtoul 3
109.Sh STANDARDS
110The
111.Fn strtod
112function conforms to
113.St -ansiC .