1.\" Copyright (c) 1990, 1991 The Regents of the University of California. 2.\" All rights reserved. 3.\" 4.\" This code is derived from software contributed to Berkeley by 5.\" the American National Standards Committee X3, on Information 6.\" Processing Systems. 7.\" 8.\" Redistribution and use in source and binary forms, with or without 9.\" modification, are permitted provided that the following conditions 10.\" are met: 11.\" 1. Redistributions of source code must retain the above copyright 12.\" notice, this list of conditions and the following disclaimer. 13.\" 2. Redistributions in binary form must reproduce the above copyright 14.\" notice, this list of conditions and the following disclaimer in the 15.\" documentation and/or other materials provided with the distribution. 16.\" 3. All advertising materials mentioning features or use of this software 17.\" must display the following acknowledgement: 18.\" This product includes software developed by the University of 19.\" California, Berkeley and its contributors. 20.\" 4. Neither the name of the University nor the names of its contributors 21.\" may be used to endorse or promote products derived from this software 22.\" without specific prior written permission. 23.\" 24.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 25.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 26.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 27.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 28.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 29.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 30.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 31.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 33.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34.\" SUCH DAMAGE. 35.\" 36.\" $OpenBSD: strtod.3,v 1.7 2000/04/20 13:50:03 aaron Exp $ 37.\" 38.Dd June 29, 1991 39.Dt STRTOD 3 40.Os 41.Sh NAME 42.Nm strtod 43.Nd convert 44.Tn ASCII 45string to double 46.Sh SYNOPSIS 47.Fd #include <stdlib.h> 48.Ft double 49.Fn strtod "const char *nptr" "char **endptr" 50.Sh DESCRIPTION 51The 52.Fn strtod 53function converts the initial portion of the string pointed to by 54.Fa nptr 55to 56.Li double 57representation. 58.Pp 59The expected form of the string is an optional plus 60.Pq Ql + 61or minus sign 62.Pq Ql - 63followed by a sequence of digits optionally containing 64a decimal-point character, optionally followed by an exponent. 65An exponent consists of an 66.Sq E 67or 68.Sq e , 69followed by an optional plus or minus sign, followed by a sequence of digits. 70.Pp 71Leading whitespace characters in the string (as defined by the 72.Xr isspace 3 73function) are skipped. 74.Sh RETURN VALUES 75The 76.Fn strtod 77function returns the converted value, if any. 78.Pp 79If 80.Fa endptr 81is not 82.Dv NULL , 83a pointer to the character after the last character used 84in the conversion is stored in the location referenced by 85.Fa endptr . 86.Pp 87If no conversion is performed, zero is returned and the value of 88.Fa nptr 89is stored in the location referenced by 90.Fa endptr . 91.Pp 92If the correct value would cause overflow, plus or minus 93.Dv HUGE_VAL 94is returned (according to the sign of the value), and 95.Er ERANGE 96is stored in 97.Va errno . 98If the correct value would cause underflow, zero is returned and 99.Er ERANGE 100is stored in 101.Va errno . 102.Sh ERRORS 103.Bl -tag -width Er 104.It Bq Er ERANGE 105Overflow or underflow occurred. 106.El 107.Sh SEE ALSO 108.Xr atof 3 , 109.Xr atoi 3 , 110.Xr atol 3 , 111.Xr strtol 3 , 112.Xr strtoul 3 113.Sh STANDARDS 114The 115.Fn strtod 116function conforms to 117.St -ansiC . 118