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.\" Copyright (c) 1990, 1991 The Regents of the University of California.
.\" All rights reserved.
.\"
.\" This code is derived from software contributed to Berkeley by
.\" the American National Standards Committee X3, on Information
.\" Processing Systems.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\" 3. Neither the name of the University nor the names of its contributors
.\" may be used to endorse or promote products derived from this software
.\" without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" $OpenBSD: strtod.3,v 1.22 2019/01/16 12:55:49 schwarze Exp $
.\"
.Dd $Mdocdate: January 16 2019 $
.Dt STRTOD 3
.Os
.Sh NAME
.Nm strtod ,
.Nm strtof ,
.Nm strtold
.Nd convert ASCII string to double, float or long double
.Sh SYNOPSIS
.In stdlib.h
.Ft double
.Fn strtod "const char *nptr" "char **endptr"
.Pp
.Ft float
.Fn strtof "const char *nptr" "char **endptr"
.Pp
.Ft long double
.Fn strtold "const char *nptr" "char **endptr"
.Sh DESCRIPTION
The
.Fn strtod
function converts the initial portion of the string pointed to by
.Fa nptr
to
.Li double
representation.
The
.Fn strtof
function converts the initial portion of the string pointed to by
.Fa nptr
to
.Li float
representation.
The
.Fn strtold
function converts the initial portion of the string pointed to by
.Fa nptr
to
.Li long double
representation.
.Pp
The expected form of the string is an optional plus
.Pq Ql +
or minus sign
.Pq Ql -
followed by a sequence of digits optionally containing
a decimal-point character, optionally followed by an exponent.
An exponent consists of an
.Sq E
or
.Sq e ,
followed by an optional plus or minus sign, followed by a sequence of digits.
.Pp
Alternatively, if the portion of the string following the optional
plus or minus sign begins with
.Dq INF
or
.Dq NAN ,
ignoring case, it is interpreted as an infinity or a quiet \*(Na,
respectively.
The syntax
.Dq NAN Ns Pq Ar s ,
where
.Ar s
is an alphanumeric string, produces the same value as the call
.Fo nan
.Qq Ar s Ns
.Fc
(respectively,
.Fo nanf
.Qq Ar s Ns
.Fc
and
.Fo nanl
.Qq Ar s Ns
.Fc ) .
.Pp
In any of the above cases, leading whitespace characters in the
string (as defined by the
.Xr isspace 3
function) are skipped.
.Sh RETURN VALUES
The
.Fn strtod ,
.Fn strtof
and
.Fn strtold
functions return the converted value, if any.
.Pp
If
.Fa endptr
is not
.Dv NULL ,
a pointer to the character after the last character used
in the conversion is stored in the location referenced by
.Fa endptr .
.Pp
If no conversion is performed, zero is returned and the value of
.Fa nptr
is stored in the location referenced by
.Fa endptr .
.Pp
If the correct value would cause overflow, plus or minus
.Dv HUGE_VAL
is returned (according to the sign of the value), and
.Er ERANGE
is stored in
.Va errno .
If the correct value would cause underflow, zero is returned and
.Er ERANGE
is stored in
.Va errno .
.Sh ERRORS
.Bl -tag -width Er
.It Bq Er ERANGE
Overflow or underflow occurred.
.El
.Sh SEE ALSO
.Xr atof 3 ,
.Xr atoi 3 ,
.Xr atol 3 ,
.Xr strtol 3 ,
.Xr strtoul 3
.Sh STANDARDS
The
.Fn strtod
function conforms to
.St -ansiC-89 .
The
.Fn strtof
and
.Fn strtold
functions conform to
.St -isoC-99 .
.Sh CAVEATS
On systems other than
.Ox ,
the
.Dv LC_NUMERIC
.Xr locale 1
category can cause parsing failures; see CAVEATS in
.Xr setlocale 3
for details.
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