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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 1.12 2008/06/13 23:50:49 jmc Exp $
33.\"
34.Dd $Mdocdate: June 13 2008 $
35.Dt STRTOD 3
36.Os
37.Sh NAME
38.Nm strtod ,
39.Nm strtof
40.Nd convert
41.Tn ASCII
42string to double or float
43.Sh SYNOPSIS
44.Fd #include <math.h>
45.Fd #include <stdlib.h>
46.Ft double
47.Fn strtod "const char *nptr" "char **endptr"
48.Pp
49.Ft float
50.Fn strtof "const char *nptr" "char **endptr"
51.Sh DESCRIPTION
52The
53.Fn strtod
54function converts the initial portion of the string pointed to by
55.Fa nptr
56to
57.Li double
58representation.
59The
60.Fn strtof
61function converts the initial portion of the string pointed to by
62.Fa nptr
63to
64.Li float
65representation.
66.Pp
67The expected form of the string is an optional plus
68.Pq Ql +
69or minus sign
70.Pq Ql -
71followed by a sequence of digits optionally containing
72a decimal-point character, optionally followed by an exponent.
73An exponent consists of an
74.Sq E
75or
76.Sq e ,
77followed by an optional plus or minus sign, followed by a sequence of digits.
78.Pp
79Leading whitespace characters in the string (as defined by the
80.Xr isspace 3
81function) are skipped.
82.Sh RETURN VALUES
83The
84.Fn strtod
85and
86.Fn strtof
87functions return the converted value, if any.
88.Pp
89If
90.Fa endptr
91is not
92.Dv NULL ,
93a pointer to the character after the last character used
94in the conversion is stored in the location referenced by
95.Fa endptr .
96.Pp
97If no conversion is performed, zero is returned and the value of
98.Fa nptr
99is stored in the location referenced by
100.Fa endptr .
101.Pp
102If the correct value would cause overflow, plus or minus
103.Dv HUGE_VAL
104is returned (according to the sign of the value), and
105.Er ERANGE
106is stored in
107.Va errno .
108If the correct value would cause underflow, zero is returned and
109.Er ERANGE
110is stored in
111.Va errno .
112.Sh ERRORS
113.Bl -tag -width Er
114.It Bq Er ERANGE
115Overflow or underflow occurred.
116.El
117.Sh SEE ALSO
118.Xr atof 3 ,
119.Xr atoi 3 ,
120.Xr atol 3 ,
121.Xr strtol 3 ,
122.Xr strtoul 3
123.Sh STANDARDS
124The
125.Fn strtod
126and
127.Fn strtof
128functions conform to
129.St -ansiC .