.\" Copyright (c) 1990, 1991, 1993 .\" The Regents of the University of California. All rights reserved. .\" .\" This code is derived from software contributed to Berkeley by .\" the American National Standards Committee X3, on Information .\" Processing Systems. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 4. Neither the name of the University nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" .\" @(#)strtod.3 8.1 (Berkeley) 6/4/93 .\" $FreeBSD: src/lib/libc/stdlib/strtod.3,v 1.22 2007/12/16 21:19:28 das Exp $ .\" .Dd March 2, 2003 .Dt STRTOD 3 .Os .Sh NAME .Nm strtod , strtof , strtold .Nd convert .Tn ASCII string to floating point .Sh LIBRARY .Lb libc .Sh SYNOPSIS .In stdlib.h .Ft double .Fo strtod .Fa "const char *restrict nptr" .Fa "char **restrict endptr" .Fc .Ft float .Fo strtof .Fa "const char *restrict nptr" .Fa "char **restrict endptr" .Fc .Ft "long double" .Fo strtold .Fa "const char *restrict nptr" .Fa "char **restrict endptr" .Fc .Sh DESCRIPTION These conversion functions convert the initial portion of the string pointed to by .Fa nptr to .Vt double , .Vt float , and .Vt "long double" representation, respectively. .Pp The expected form of the string is an optional plus (``+'') or minus (``\-'') sign, followed by either: .Bl -bullet .It a decimal significand, consisting of a sequence of decimal digits (optionally containing a decimal-point character) or .It a hexadecimal significand, consisting of a ``0X'' or ``0x'' followed by a sequence of hexadecimal digits (optionally containing a decimal-point character). .El .Pp In both cases, the significand may be optionally followed by an exponent. An exponent consists of an ``E'' or ``e'' (for decimal constants) or a ``P'' or ``p'' (for hexadecimal constants), followed by an optional plus or minus sign, followed by a sequence of decimal digits. For decimal constants, the exponent indicates the power of 10 by which the significand should be scaled. For hexadecimal constants, the scaling is instead done by powers of 2. .Pp Alternatively, if the portion of the string following the optional plus or minus sign begins with .Dq INFINITY or .Dq NAN , ignoring case, it is interpreted as an infinity or a quiet \*(Na, respectively. The syntax .Dq Xo Pf NAN( Ar "s" ) Xc , where .Ar s is an alphanumeric string, produces the same value as the call .Fo nan .Qq Ar s Ns .Fc (respectively, .Fo nanf .Qq Ar s Ns .Fc and .Fo nanl .Qq Ar s Ns .Fc . ) .Pp In any of the above cases, leading white-space characters in the string (as defined by the .Xr isspace 3 function) are skipped. The decimal point character is defined in the program's locale (category .Dv LC_NUMERIC ) . .Pp Extended locale versions of these functions are documented in .Xr strtod_l 3 . See .Xr xlocale 3 for more information. .Sh RETURN VALUES The .Fn strtod , .Fn strtof , and .Fn strtold functions return the converted value, if any. .Pp If .Fa endptr is not .Dv NULL , a pointer to the character after the last character used in the conversion is stored in the location referenced by .Fa endptr . .Pp If no conversion is performed, zero is returned and the value of .Fa nptr is stored in the location referenced by .Fa endptr . .Pp If the correct value would cause overflow, plus or minus .Dv HUGE_VAL , .Dv HUGE_VALF , or .Dv HUGE_VALL is returned (according to the sign and type of the return value), and .Er ERANGE is stored in .Va errno . If the correct value would cause underflow, zero is returned and .Er ERANGE is stored in .Va errno . .Sh ERRORS .Bl -tag -width Er .It Bq Er ERANGE Overflow or underflow occurred. .El .Sh SEE ALSO .Xr atof 3 , .Xr atoi 3 , .Xr atol 3 , .Xr nan 3 , .Xr strtod_l 3 , .Xr strtol 3 , .Xr strtoul 3 , .Xr wcstod 3 .Sh STANDARDS The .Fn strtod function conforms to .St -isoC-99 . .Sh AUTHORS The author of this software is .An David M. Gay . .Pp .Bd -literal Copyright (c) 1998 by Lucent Technologies All Rights Reserved Permission to use, copy, modify, and distribute this software and its documentation for any purpose and without fee is hereby granted, provided that the above copyright notice appear in all copies and that both that the copyright notice and this permission notice and warranty disclaimer appear in supporting documentation, and that the name of Lucent or any of its entities not be used in advertising or publicity pertaining to distribution of the software without specific, written prior permission. LUCENT DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL LUCENT OR ANY OF ITS ENTITIES BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. .Ed