stdlib/FreeBSD/strtod.3

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  32 .\"     @(#)strtod.3    8.1 (Berkeley) 6/4/93
  33 .\" $FreeBSD: src/lib/libc/stdlib/strtod.3,v 1.22 2007/12/16 21:19:28 das Exp $
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  35 .Dd March 2, 2003
  36 .Dt STRTOD 3
  37 .Os
  38 .Sh NAME
  39 .Nm strtod , strtof , strtold
  40 .Nd convert
  41 .Tn ASCII
  42 string to floating point
  43 .Sh LIBRARY
  44 .Lb libc
  45 .Sh SYNOPSIS
  46 .In stdlib.h
  47 .Ft double
  48 .Fn strtod "const char * restrict nptr" "char ** restrict endptr"
  49 .Ft float
  50 .Fn strtof "const char * restrict nptr" "char ** restrict endptr"
  51 .Ft "long double"
  52 .Fn strtold "const char * restrict nptr" "char ** restrict endptr"
  53 .Sh DESCRIPTION
  54 These conversion
  55 functions convert the initial portion of the string
  56 pointed to by
  57 .Fa nptr
  58 to
  59 .Vt double ,
  60 .Vt float ,
  61 and
  62 .Vt "long double"
  63 representation, respectively.
  64 .Pp
  65 The expected form of the string is an optional plus (``+'') or minus
  66 sign (``\-'') followed by either:
  67 .Bl -bullet
  68 .It
  69 a decimal significand consisting of a sequence of decimal digits
  70 optionally containing a decimal-point character, or
  71 .It
  72 a hexadecimal significand consisting of a ``0X'' or ``0x'' followed
  73 by a sequence of hexadecimal digits optionally containing a
  74 decimal-point character.
  75 .El
  76 .Pp
  77 In both cases, the significand may be optionally followed by an
  78 exponent.
  79 An exponent consists of an ``E'' or ``e'' (for decimal
  80 constants) or a ``P'' or ``p'' (for hexadecimal constants),
  81 followed by an optional plus or minus sign, followed by a
  82 sequence of decimal digits.
  83 For decimal constants, the exponent indicates the power of 10 by
  84 which the significand should be scaled.
  85 For hexadecimal constants, the scaling is instead done by powers
  86 of 2.
  87 .Pp
  88 Alternatively, if the portion of the string following the optional
  89 plus or minus sign begins with
  90 .Dq INFINITY
  91 or
  92 .Dq NAN ,
  93 ignoring case, it is interpreted as an infinity or a quiet \*(Na,
  94 respectively.
  95 The syntax
  96 .Dq Xo Pf NAN( Ar "s" ) Xc ,
  97 where
  98 .Ar s
  99 is an alphanumeric string, produces the same value as the call
 100 .Fo nan
 101 .Qq Ar s Ns
 102 .Fc
 103 (respectively,
 104 .Fo nanf
 105 .Qq Ar s Ns
 106 .Fc
 107 and
 108 .Fo nanl
 109 .Qq Ar s Ns
 110 .Fc . )
 111 .Pp
 112 In any of the above cases, leading white-space characters in the
 113 string (as defined by the
 114 .Xr isspace 3
 115 function) are skipped.
 116 The decimal point
 117 character is defined in the program's locale (category
 118 .Dv LC_NUMERIC ) .
 119 .Sh RETURN VALUES
 120 The
 121 .Fn strtod ,
 122 .Fn strtof ,
 123 and
 124 .Fn strtold
 125 functions return the converted value, if any.
 126 .Pp
 127 If
 128 .Fa endptr
 129 is not
 130 .Dv NULL ,
 131 a pointer to the character after the last character used
 132 in the conversion is stored in the location referenced by
 133 .Fa endptr .
 134 .Pp
 135 If no conversion is performed, zero is returned and the value of
 136 .Fa nptr
 137 is stored in the location referenced by
 138 .Fa endptr .
 139 .Pp
 140 If the correct value would cause overflow, plus or minus
 141 .Dv HUGE_VAL ,
 142 .Dv HUGE_VALF ,
 143 or
 144 .Dv HUGE_VALL
 145 is returned (according to the sign and type of the return value), and
 146 .Er ERANGE
 147 is stored in
 148 .Va errno .
 149 If the correct value would cause underflow, zero is
 150 returned and
 151 .Er ERANGE
 152 is stored in
 153 .Va errno .
 154 .Sh ERRORS
 155 .Bl -tag -width Er
 156 .It Bq Er ERANGE
 157 Overflow or underflow occurred.
 158 .El
 159 .Sh SEE ALSO
 160 .Xr atof 3 ,
 161 .Xr atoi 3 ,
 162 .Xr atol 3 ,
 163 .Xr nan 3 ,
 164 .Xr strtol 3 ,
 165 .Xr strtoul 3 ,
 166 .Xr wcstod 3
 167 .Sh STANDARDS
 168 The
 169 .Fn strtod
 170 function
 171 conforms to
 172 .St -isoC-99 ,
 173 with the exception of the bug noted below.
 174 .Sh AUTHORS
 175 The author of this software is
 176 .An David M. Gay .
 177 .Pp
 178 .Bd -literal
 179 Copyright (c) 1998 by Lucent Technologies
 180 All Rights Reserved
 181
 182 Permission to use, copy, modify, and distribute this software and
 183 its documentation for any purpose and without fee is hereby
 184 granted, provided that the above copyright notice appear in all
 185 copies and that both that the copyright notice and this
 186 permission notice and warranty disclaimer appear in supporting
 187 documentation, and that the name of Lucent or any of its entities
 188 not be used in advertising or publicity pertaining to
 189 distribution of the software without specific, written prior
 190 permission.
 191
 192 LUCENT DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
 193 INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS.
 194 IN NO EVENT SHALL LUCENT OR ANY OF ITS ENTITIES BE LIABLE FOR ANY
 195 SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 196 WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER
 197 IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
 198 ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF
 199 THIS SOFTWARE.
 200 .Ed