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 .Fo strtod
  49 .Fa "const char *restrict nptr"
  50 .Fa "char **restrict endptr"
  51 .Fc
  52 .Ft float
  53 .Fo strtof
  54 .Fa "const char *restrict nptr"
  55 .Fa "char **restrict endptr"
  56 .Fc
  57 .Ft "long double"
  58 .Fo strtold
  59 .Fa "const char *restrict nptr"
  60 .Fa "char **restrict endptr"
  61 .Fc
  62 .Sh DESCRIPTION
  63 These conversion
  64 functions convert the initial portion of the string
  65 pointed to by
  66 .Fa nptr
  67 to
  68 .Vt double ,
  69 .Vt float ,
  70 and
  71 .Vt "long double"
  72 representation, respectively.
  73 .Pp
  74 The expected form of the string
  75 is an optional plus (``+'') or minus (``\-'') sign,
  76 followed by either:
  77 .Bl -bullet
  78 .It
  79 a decimal significand, consisting of a sequence of decimal digits
  80 (optionally containing a decimal-point character) or
  81 .It
  82 a hexadecimal significand, consisting of a ``0X'' or ``0x'' followed
  83 by a sequence of hexadecimal digits
  84 (optionally containing a decimal-point character).
  85 .El
  86 .Pp
  87 In both cases, the significand may be optionally followed by an
  88 exponent.
  89 An exponent consists of an ``E'' or ``e'' (for decimal
  90 constants) or a ``P'' or ``p'' (for hexadecimal constants),
  91 followed by an optional plus or minus sign, followed by a
  92 sequence of decimal digits.
  93 For decimal constants, the exponent indicates the power of 10 by
  94 which the significand should be scaled.
  95 For hexadecimal constants, the scaling is instead done by powers
  96 of 2.
  97 .Pp
  98 Alternatively, if the portion of the string following the optional
  99 plus or minus sign begins with
 100 .Dq INFINITY
 101 or
 102 .Dq NAN ,
 103 ignoring case, it is interpreted as an infinity or a quiet \*(Na,
 104 respectively.
 105 The syntax
 106 .Dq Xo Pf NAN( Ar "s" ) Xc ,
 107 where
 108 .Ar s
 109 is an alphanumeric string, produces the same value as the call
 110 .Fo nan
 111 .Qq Ar s Ns
 112 .Fc
 113 (respectively,
 114 .Fo nanf
 115 .Qq Ar s Ns
 116 .Fc
 117 and
 118 .Fo nanl
 119 .Qq Ar s Ns
 120 .Fc . )
 121 .Pp
 122 In any of the above cases, leading white-space characters in the
 123 string (as defined by the
 124 .Xr isspace 3
 125 function) are skipped.
 126 The decimal point
 127 character is defined in the program's locale (category
 128 .Dv LC_NUMERIC ) .
 129 .Pp
 130 Extended locale versions of these functions are documented in
 131 .Xr strtod_l 3 .
 132 See
 133 .Xr xlocale 3
 134 for more information.
 135 .Sh RETURN VALUES
 136 The
 137 .Fn strtod ,
 138 .Fn strtof ,
 139 and
 140 .Fn strtold
 141 functions return the converted value, if any.
 142 .Pp
 143 If
 144 .Fa endptr
 145 is not
 146 .Dv NULL ,
 147 a pointer to the character after the last character used
 148 in the conversion is stored in the location referenced by
 149 .Fa endptr .
 150 .Pp
 151 If no conversion is performed, zero is returned and the value of
 152 .Fa nptr
 153 is stored in the location referenced by
 154 .Fa endptr .
 155 .Pp
 156 If the correct value would cause overflow, plus or minus
 157 .Dv HUGE_VAL ,
 158 .Dv HUGE_VALF ,
 159 or
 160 .Dv HUGE_VALL
 161 is returned (according to the sign and type of the return value), and
 162 .Er ERANGE
 163 is stored in
 164 .Va errno .
 165 If the correct value would cause underflow, zero is
 166 returned and
 167 .Er ERANGE
 168 is stored in
 169 .Va errno .
 170 .Sh ERRORS
 171 .Bl -tag -width Er
 172 .It Bq Er ERANGE
 173 Overflow or underflow occurred.
 174 .El
 175 .Sh SEE ALSO
 176 .Xr atof 3 ,
 177 .Xr atoi 3 ,
 178 .Xr atol 3 ,
 179 .Xr nan 3 ,
 180 .Xr strtod_l 3 ,
 181 .Xr strtol 3 ,
 182 .Xr strtoul 3 ,
 183 .Xr wcstod 3
 184 .Sh STANDARDS
 185 The
 186 .Fn strtod
 187 function
 188 conforms to
 189 .St -isoC-99 .
 190 .Sh AUTHORS
 191 The author of this software is
 192 .An David M. Gay .
 193 .Pp
 194 .Bd -literal
 195 Copyright (c) 1998 by Lucent Technologies
 196 All Rights Reserved
 197
 198 Permission to use, copy, modify, and distribute this software and
 199 its documentation for any purpose and without fee is hereby
 200 granted, provided that the above copyright notice appear in all
 201 copies and that both that the copyright notice and this
 202 permission notice and warranty disclaimer appear in supporting
 203 documentation, and that the name of Lucent or any of its entities
 204 not be used in advertising or publicity pertaining to
 205 distribution of the software without specific, written prior
 206 permission.
 207
 208 LUCENT DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
 209 INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS.
 210 IN NO EVENT SHALL LUCENT OR ANY OF ITS ENTITIES BE LIABLE FOR ANY
 211 SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 212 WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER
 213 IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
 214 ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF
 215 THIS SOFTWARE.
 216 .Ed