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. 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.\" $OpenBSD: strtod.3,v 1.22 2019/01/16 12:55:49 schwarze Exp $ 33.\" 34.Dd $Mdocdate: January 16 2019 $ 35.Dt STRTOD 3 36.Os 37.Sh NAME 38.Nm strtod , 39.Nm strtof , 40.Nm strtold 41.Nd convert ASCII string to double, float or long double 42.Sh SYNOPSIS 43.In stdlib.h 44.Ft double 45.Fn strtod "const char *nptr" "char **endptr" 46.Pp 47.Ft float 48.Fn strtof "const char *nptr" "char **endptr" 49.Pp 50.Ft long double 51.Fn strtold "const char *nptr" "char **endptr" 52.Sh DESCRIPTION 53The 54.Fn strtod 55function converts the initial portion of the string pointed to by 56.Fa nptr 57to 58.Li double 59representation. 60The 61.Fn strtof 62function converts the initial portion of the string pointed to by 63.Fa nptr 64to 65.Li float 66representation. 67The 68.Fn strtold 69function converts the initial portion of the string pointed to by 70.Fa nptr 71to 72.Li long double 73representation. 74.Pp 75The expected form of the string is an optional plus 76.Pq Ql + 77or minus sign 78.Pq Ql - 79followed by a sequence of digits optionally containing 80a decimal-point character, optionally followed by an exponent. 81An exponent consists of an 82.Sq E 83or 84.Sq e , 85followed by an optional plus or minus sign, followed by a sequence of digits. 86.Pp 87Alternatively, if the portion of the string following the optional 88plus or minus sign begins with 89.Dq INF 90or 91.Dq NAN , 92ignoring case, it is interpreted as an infinity or a quiet \*(Na, 93respectively. 94The syntax 95.Dq NAN Ns Pq Ar s , 96where 97.Ar s 98is an alphanumeric string, produces the same value as the call 99.Fo nan 100.Qq Ar s Ns 101.Fc 102(respectively, 103.Fo nanf 104.Qq Ar s Ns 105.Fc 106and 107.Fo nanl 108.Qq Ar s Ns 109.Fc ) . 110.Pp 111In any of the above cases, leading whitespace characters in the 112string (as defined by the 113.Xr isspace 3 114function) are skipped. 115.Sh RETURN VALUES 116The 117.Fn strtod , 118.Fn strtof 119and 120.Fn strtold 121functions return the converted value, if any. 122.Pp 123If 124.Fa endptr 125is not 126.Dv NULL , 127a pointer to the character after the last character used 128in the conversion is stored in the location referenced by 129.Fa endptr . 130.Pp 131If no conversion is performed, zero is returned and the value of 132.Fa nptr 133is stored in the location referenced by 134.Fa endptr . 135.Pp 136If the correct value would cause overflow, plus or minus 137.Dv HUGE_VAL 138is returned (according to the sign of the value), and 139.Er ERANGE 140is stored in 141.Va errno . 142If the correct value would cause underflow, zero is returned and 143.Er ERANGE 144is stored in 145.Va errno . 146.Sh ERRORS 147.Bl -tag -width Er 148.It Bq Er ERANGE 149Overflow or underflow occurred. 150.El 151.Sh SEE ALSO 152.Xr atof 3 , 153.Xr atoi 3 , 154.Xr atol 3 , 155.Xr strtol 3 , 156.Xr strtoul 3 157.Sh STANDARDS 158The 159.Fn strtod 160function conforms to 161.St -ansiC-89 . 162The 163.Fn strtof 164and 165.Fn strtold 166functions conform to 167.St -isoC-99 . 168.Sh CAVEATS 169On systems other than 170.Ox , 171the 172.Dv LC_NUMERIC 173.Xr locale 1 174category can cause parsing failures; see CAVEATS in 175.Xr setlocale 3 176for details. 177