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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 1.19 2014/01/19 10:39:00 schwarze Exp $
+.\"
+.Dd $Mdocdate: January 19 2014 $
+.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 -ansiC-99 .