1.\" $NetBSD: strtod.3,v 1.20 2007/10/24 13:42:10 reed 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. Neither the name of the University nor the names of its contributors 19.\" may be used to endorse or promote products derived from this software 20.\" without specific prior written permission. 21.\" 22.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32.\" SUCH DAMAGE. 33.\" 34.\" from: @(#)strtod.3 8.1 (Berkeley) 6/4/93 35.\" 36.Dd March 12, 2006 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 double, float, or long double 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 57The 58.Fn strtod 59function converts the initial portion of the string 60pointed to by 61.Fa nptr 62to 63.Em double 64representation. 65.Pp 66The 67.Fn strtof 68function converts the initial portion of the string 69pointed to by 70.Fa nptr 71to 72.Em float 73representation. 74.Pp 75The 76.Fn strtold 77function converts the initial portion of the string 78pointed to by 79.Fa nptr 80to 81.Em long double 82representation. 83.Pp 84The expected form of the string is an optional plus 85.Pq Sq + 86or minus sign 87.Pq Sq \- 88followed by one of the following: 89.Bl -dash 90.It 91a sequence of digits optionally containing 92a decimal-point character, optionally followed by an exponent. 93An exponent consists of an 94.Sq E 95or 96.Sq e , 97followed by an optional plus 98or minus sign, followed by a sequence of digits. 99.It 100one of 101.Li INF 102or 103.Li INFINITY , 104ignoring case. 105.It 106one of 107.Li NAN 108or 109.Li NAN(n-char-sequence-opt) , 110ignoring case. 111This implementation currently does not interpret such a sequence. 112.El 113.Pp 114Leading white-space characters in the string (as defined by the 115.Xr isspace 3 116function) are skipped. 117.Sh RETURN VALUES 118The 119.Fn strtod , 120.Fn strtof , 121and 122.Fn strtold 123functions return the converted value, if any. 124.Pp 125A character sequence 126.Li INF 127or 128.Li INFINITY 129is converted to \*(If, 130if supported, else to the largest finite floating-point number representable 131on the machine (i.e., 132.Tn VAX ) . 133.Pp 134A character sequence 135.Li NAN 136or 137.Li NAN(n-char-sequence-opt) 138is converted to a quiet \*(Na, if supported, else remains unrecognized (i.e., 139.Tn VAX ) . 140.Pp 141If 142.Fa endptr 143is not 144.Dv NULL , 145a pointer to the character after the last character used 146in the conversion is stored in the location referenced by 147.Fa endptr . 148.Pp 149If no conversion is performed, zero is returned and the value of 150.Fa nptr 151is stored in the location referenced by 152.Fa endptr . 153.Pp 154If the correct value would cause overflow, plus or minus 155.Dv HUGE_VAL , 156.Dv HUGE_VALF , 157or 158.Dv HUGE_VALL 159is returned (according to the return type and sign of the value), and 160.Dv ERANGE 161is stored in 162.Va errno . 163If the correct value would cause underflow, zero is 164returned and 165.Dv ERANGE 166is stored in 167.Va errno . 168.Sh ERRORS 169.Bl -tag -width Er 170.It Bq Er ERANGE 171Overflow or underflow occurred. 172.El 173.Sh SEE ALSO 174.Xr atof 3 , 175.Xr atoi 3 , 176.Xr atol 3 , 177.Xr math 3 , 178.Xr strtol 3 , 179.Xr strtoul 3 180.Sh STANDARDS 181The 182.Fn strtod 183function 184conforms to 185.St -ansiC . 186The 187.Fn strtof 188and 189.Fn strtold 190functions conform to 191.St -isoC-99 . 192.Sh HISTORY 193The 194.Fn strtof 195and 196.Fn strtold 197functions appeared in 198.Nx 4.0 . 199