.\" Copyright (c) 1990, 1991 The Regents of the University of California.
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.\" This code is derived from software contributed to Berkeley by
.\" the American National Standards Committee X3, on Information
.\" Processing Systems.
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.\"	$OpenBSD: strtod.3,v 1.8 2003/06/02 20:18:38 millert Exp $
.\"
.Dd June 29, 1991
.Dt STRTOD 3
.Os
.Sh NAME
.Nm strtod
.Nd convert
.Tn ASCII
string to double
.Sh SYNOPSIS
.Fd #include <stdlib.h>
.Ft double
.Fn strtod "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.
.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
Leading whitespace characters in the string (as defined by the
.Xr isspace 3
function) are skipped.
.Sh RETURN VALUES
The
.Fn strtod
function returns 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 .