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.\" Copyright (c) 1990, 1991 The Regents of the University of California.
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.\" All rights reserved.
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.\"
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.\" This code is derived from software contributed to Berkeley by
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.\" the American National Standards Committee X3, on Information
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.\" Processing Systems.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $OpenBSD: strtod.3,v 1.15 2012/09/15 11:47:04 martynas Exp $
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.\"
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.Dd $Mdocdate: September 15 2012 $
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.Dt STRTOD 3
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.Os
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.Sh NAME
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.Nm strtod ,
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.Nm strtof ,
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.Nm strtold
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.Nd convert
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.Tn ASCII
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string to double, float or long double
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.Sh SYNOPSIS
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.Fd #include <math.h>
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.Fd #include <stdlib.h>
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.Ft double
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.Fn strtod "const char *nptr" "char **endptr"
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.Pp
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.Ft float
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.Fn strtof "const char *nptr" "char **endptr"
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.Pp
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.Ft long double
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.Fn strtold "const char *nptr" "char **endptr"
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.Sh DESCRIPTION
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The
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.Fn strtod
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function converts the initial portion of the string pointed to by
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.Fa nptr
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to
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.Li double
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representation.
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The
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.Fn strtof
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function converts the initial portion of the string pointed to by
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.Fa nptr
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to
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.Li float
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representation.
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The
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.Fn strtold
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function converts the initial portion of the string pointed to by
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.Fa nptr
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to
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.Li long double
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representation.
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.Pp
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The expected form of the string is an optional plus
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.Pq Ql +
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or minus sign
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.Pq Ql -
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followed by a sequence of digits optionally containing
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a decimal-point character, optionally followed by an exponent.
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An exponent consists of an
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.Sq E
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or
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.Sq e ,
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followed by an optional plus or minus sign, followed by a sequence of digits.
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.Pp
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Alternatively, if the portion of the string following the optional
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plus or minus sign begins with
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.Dq INF
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or
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.Dq NAN ,
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ignoring case, it is interpreted as an infinity or a quiet \*(Na,
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respectively.
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The syntax
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.Dq Xo Pf NAN( Ar "s" ) Xc ,
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where
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.Ar s
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is an alphanumeric string, produces the same value as the call
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.Fo nan
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.Qq Ar s Ns
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.Fc
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(respectively,
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.Fo nanf
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.Qq Ar s Ns
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.Fc
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and
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.Fo nanl
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.Qq Ar s Ns
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.Fc . )
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.Pp
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In any of the above cases, leading whitespace characters in the
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string (as defined by the
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.Xr isspace 3
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function) are skipped.
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.Sh RETURN VALUES
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The
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.Fn strtod ,
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.Fn strtof
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and
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.Fn strtold
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functions return the converted value, if any.
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.Pp
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If
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.Fa endptr
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is not
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.Dv NULL ,
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a pointer to the character after the last character used
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in the conversion is stored in the location referenced by
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.Fa endptr .
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.Pp
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If no conversion is performed, zero is returned and the value of
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.Fa nptr
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is stored in the location referenced by
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.Fa endptr .
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.Pp
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If the correct value would cause overflow, plus or minus
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.Dv HUGE_VAL
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is returned (according to the sign of the value), and
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.Er ERANGE
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is stored in
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.Va errno .
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If the correct value would cause underflow, zero is returned and
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.Er ERANGE
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is stored in
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.Va errno .
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.Sh ERRORS
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.Bl -tag -width Er
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.It Bq Er ERANGE
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Overflow or underflow occurred.
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.El
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.Sh SEE ALSO
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.Xr atof 3 ,
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.Xr atoi 3 ,
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.Xr atol 3 ,
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.Xr strtol 3 ,
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.Xr strtoul 3
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.Sh STANDARDS
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The
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.Fn strtod
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function conforms to
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.St -ansiC-89 .
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The
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.Fn strtof
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and
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.Fn strtold
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functions conform to
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.St -ansiC-99 .
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