1.\" Copyright (c) 1990, 1991, 1993 2.\" The Regents of the University of California. 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.\" 4. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" @(#)strtod.3 8.1 (Berkeley) 6/4/93 33.\" $FreeBSD: src/lib/libc/stdlib/strtod.3,v 1.21 2007/01/09 00:28:10 imp Exp $ 34.\" $DragonFly: src/lib/libc/stdlib/strtod.3,v 1.2 2003/06/17 04:26:46 dillon Exp $ 35.\" 36.Dd March 2, 2003 37.Dt STRTOD 3 38.Os 39.Sh NAME 40.Nm strtod , 41.Nm strtof , 42.Nm strtold 43.Nd convert 44.Tn ASCII 45string to floating point 46.Sh LIBRARY 47.Lb libc 48.Sh SYNOPSIS 49.In stdlib.h 50.Ft double 51.Fn strtod "const char * restrict nptr" "char ** restrict endptr" 52.Ft float 53.Fn strtof "const char * restrict nptr" "char ** restrict endptr" 54.Ft "long double" 55.Fn strtold "const char * restrict nptr" "char ** restrict endptr" 56.Sh DESCRIPTION 57These conversion 58functions convert the initial portion of the string 59pointed to by 60.Fa nptr 61to 62.Vt double , 63.Vt float , 64and 65.Vt "long double" 66representation, respectively. 67.Pp 68The expected form of the string is an optional plus (``+'') or minus 69sign (``\-'') followed by either: 70.Bl -bullet 71.It 72a decimal significand consisting of a sequence of decimal digits 73optionally containing a decimal-point character, or 74.It 75a hexadecimal significand consisting of a ``0X'' or ``0x'' followed 76by a sequence of hexadecimal digits optionally containing a 77decimal-point character. 78.El 79.Pp 80In both cases, the significand may be optionally followed by an 81exponent. 82An exponent consists of an ``E'' or ``e'' (for decimal 83constants) or a ``P'' or ``p'' (for hexadecimal constants), 84followed by an optional plus or minus sign, followed by a 85sequence of decimal digits. 86For decimal constants, the exponent indicates the power of 10 by 87which the significand should be scaled. 88For hexadecimal constants, the scaling is instead done by powers 89of 2. 90.Pp 91Alternatively, if the portion of the string following the optional 92plus or minus sign begins with ``INFINITY'' or ``NAN'', ignoring 93case, it is interpreted as an infinity or a quiet NaN, respectively. 94.Pp 95In any of the above cases, leading white-space characters in the 96string (as defined by the 97.Xr isspace 3 98function) are skipped. 99The decimal point 100character is defined in the program's locale (category 101.Dv LC_NUMERIC ) . 102.Sh RETURN VALUES 103The 104.Fn strtod , 105.Fn strtof , 106and 107.Fn strtold 108functions return the converted value, if any. 109.Pp 110If 111.Fa endptr 112is not 113.Dv NULL , 114a pointer to the character after the last character used 115in the conversion is stored in the location referenced by 116.Fa endptr . 117.Pp 118If no conversion is performed, zero is returned and the value of 119.Fa nptr 120is stored in the location referenced by 121.Fa endptr . 122.Pp 123If the correct value would cause overflow, plus or minus 124.Dv HUGE_VAL , 125.Dv HUGE_VALF , 126or 127.Dv HUGE_VALL 128is returned (according to the sign and type of the return value), and 129.Er ERANGE 130is stored in 131.Va errno . 132If the correct value would cause underflow, zero is 133returned and 134.Er 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 strtol 3 , 147.Xr strtoul 3 , 148.Xr wcstod 3 149.Sh STANDARDS 150The 151.Fn strtod 152function 153conforms to 154.St -isoC-99 , 155with the exception of the bug noted below. 156.Sh AUTHORS 157The author of this software is 158.An David M. Gay . 159.Bd -literal 160Copyright (c) 1998 by Lucent Technologies 161All Rights Reserved 162 163Permission to use, copy, modify, and distribute this software and 164its documentation for any purpose and without fee is hereby 165granted, provided that the above copyright notice appear in all 166copies and that both that the copyright notice and this 167permission notice and warranty disclaimer appear in supporting 168documentation, and that the name of Lucent or any of its entities 169not be used in advertising or publicity pertaining to 170distribution of the software without specific, written prior 171permission. 172 173LUCENT DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, 174INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. 175IN NO EVENT SHALL LUCENT OR ANY OF ITS ENTITIES BE LIABLE FOR ANY 176SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 177WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER 178IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, 179ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF 180THIS SOFTWARE. 181.Ed 182.Sh BUGS 183These routines do not recognize the C99 ``NaN(...)'' syntax. 184