1.\" $NetBSD: strtod.3,v 1.13 2002/02/07 07:00:30 ross Exp $ 2.\" 3.\" Copyright (c) 1990, 1991, 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" This code is derived from software contributed to Berkeley by 7.\" the American National Standards Committee X3, on Information 8.\" Processing Systems. 9.\" 10.\" Redistribution and use in source and binary forms, with or without 11.\" modification, are permitted provided that the following conditions 12.\" are met: 13.\" 1. Redistributions of source code must retain the above copyright 14.\" notice, this list of conditions and the following disclaimer. 15.\" 2. Redistributions in binary form must reproduce the above copyright 16.\" notice, this list of conditions and the following disclaimer in the 17.\" documentation and/or other materials provided with the distribution. 18.\" 3. All advertising materials mentioning features or use of this software 19.\" must display the following acknowledgement: 20.\" This product includes software developed by the University of 21.\" California, Berkeley and its contributors. 22.\" 4. Neither the name of the University nor the names of its contributors 23.\" may be used to endorse or promote products derived from this software 24.\" without specific prior written permission. 25.\" 26.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 27.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 28.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 29.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 30.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 31.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 32.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 33.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 34.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 35.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 36.\" SUCH DAMAGE. 37.\" 38.\" from: @(#)strtod.3 8.1 (Berkeley) 6/4/93 39.\" 40.Dd January 28, 2002 41.Dt STRTOD 3 42.Os 43.Sh NAME 44.Nm strtod 45.Nd convert 46.Tn ASCII 47string to double 48.Sh LIBRARY 49.Lb libc 50.Sh SYNOPSIS 51.Fd #include \*[Lt]stdlib.h\*[Gt] 52.Ft double 53.Fn strtod "const char * restrict nptr" "char ** restrict endptr" 54.Sh DESCRIPTION 55The 56.Fn strtod 57function converts the initial portion of the string 58pointed to by 59.Fa nptr 60to 61.Em double 62representation. 63.Pp 64The expected form of the string is an optional plus (``+'') or minus 65sign (``\-'') followed by one of the following: 66.Bl -dash 67.It 68a sequence of digits optionally containing 69a decimal-point character, optionally followed by an exponent. 70An exponent consists of an ``E'' or ``e'', followed by an optional plus 71or minus sign, followed by a sequence of digits. 72.It 73one of 74.Li INF 75or 76.Li INFINITY , 77ignoring case. 78.It 79one of 80.Li NAN 81or 82.Li NAN(n-char-sequence-opt) , 83ignoring case. 84This implementation currently does not interpret such a sequence. 85.El 86.Pp 87Leading white-space characters in the string (as defined by the 88.Xr isspace 3 89function) are skipped. 90.Sh RETURN VALUES 91The 92.Fn strtod 93function returns the converted value, if any. 94.Pp 95A character sequence 96.Li INF 97or 98.Li INFINITY 99is converted to \*(If, 100if supported, else to the largest finite floating-point number representable 101on the machine (i.e., 102.Tn VAX ) . 103.Pp 104A character sequence 105.Li NAN 106or 107.Li NAN(n-char-sequence-opt) 108is converted to a quiet \*(Na, if supported, else to a 109.Dq reserved operand 110for that machine (i.e., 111.Tn VAX ) . 112.Pp 113If 114.Fa endptr 115is not 116.Dv NULL , 117a pointer to the character after the last character used 118in the conversion is stored in the location referenced by 119.Fa endptr . 120.Pp 121If no conversion is performed, zero is returned and the value of 122.Fa nptr 123is stored in the location referenced by 124.Fa endptr . 125.Pp 126If the correct value would cause overflow, plus or minus 127.Dv HUGE_VAL 128is returned (according to the sign of the value), and 129.Dv ERANGE 130is stored in 131.Va errno . 132If the correct value would cause underflow, zero is 133returned and 134.Dv ERANGE 135is stored in 136.Va errno . 137.Sh ERRORS 138.Bl -tag -width Er 139.It Bq Er ERANGE 140Overflow or underflow occurred. 141.El 142.Sh SEE ALSO 143.Xr atof 3 , 144.Xr atoi 3 , 145.Xr atol 3 , 146.Xr math 3 , 147.Xr strtol 3 , 148.Xr strtoul 3 149.Sh STANDARDS 150The 151.Fn strtod 152function 153conforms to 154.St -ansiC . 155