stdlib/strtod.3

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  36 .\"     @(#)strtod.3    8.1 (Berkeley) 6/4/93
  37 .\" $FreeBSD: src/lib/libc/stdlib/strtod.3,v 1.19 2003/05/22 13:02:28 ru Exp $
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  39 .Dd March 2, 2003
  40 .Dt STRTOD 3
  41 .Os
  42 .Sh NAME
  43 .Nm strtod , strtof , strtold
  44 .Nd convert
  45 .Tn ASCII
  46 string to floating point
  47 .Sh LIBRARY
  48 .Lb libc
  49 .Sh SYNOPSIS
  50 .In stdlib.h
  51 .Ft double
  52 .Fo strtod
  53 .Fa "const char *restrict nptr"
  54 .Fa "char **restrict endptr"
  55 .Fc
  56 .Ft float
  57 .Fo strtof
  58 .Fa "const char *restrict nptr"
  59 .Fa "char **restrict endptr"
  60 .Fc
  61 .Ft "long double"
  62 .Fo strtold
  63 .Fa "const char *restrict nptr"
  64 .Fa "char **restrict endptr"
  65 .Fc
  66 .Sh DESCRIPTION
  67 These conversion
  68 functions convert the initial portion of the string
  69 pointed to by
  70 .Fa nptr
  71 to
  72 .Vt double ,
  73 .Vt float ,
  74 and
  75 .Vt "long double"
  76 representation, respectively.
  77 .Pp
  78 The expected form of the string
  79 is an optional plus (``+'') or minus (``\-'') sign,
  80 followed by either:
  81 .Bl -bullet
  82 .It
  83 a decimal significand, consisting of a sequence of decimal digits
  84 (optionally containing a decimal-point character) or
  85 .It
  86 a hexadecimal significand, consisting of a ``0X'' or ``0x'' followed
  87 by a sequence of hexadecimal digits
  88 (optionally containing a decimal-point character).
  89 .El
  90 .Pp
  91 In both cases, the significand may be optionally followed by an
  92 exponent.
  93 An exponent consists of an ``E'' or ``e'' (for decimal
  94 constants) or a ``P'' or ``p'' (for hexadecimal constants),
  95 followed by an optional plus or minus sign, followed by a
  96 sequence of decimal digits.
  97 For decimal constants, the exponent indicates the power of 10 by
  98 which the significand should be scaled.
  99 For hexadecimal constants, the scaling is instead done by powers
 100 of 2.
 101 .Pp
 102 Alternatively, if the portion of the string following the optional
 103 plus or minus sign begins with ``INFINITY'' or ``NAN'', ignoring
 104 case, it is interpreted as an infinity or a quiet NaN, respectively.
 105 .Pp
 106 In any of the above cases, leading white-space characters in the
 107 string (as defined by the
 108 .Xr isspace 3
 109 function) are skipped.
 110 The decimal point
 111 character is defined in the program's locale (category
 112 .Dv LC_NUMERIC ) .
 113 .Pp
 114 Extended locale versions of these functions are documented in
 115 .Xr strtod_l 3 .
 116 See
 117 .Xr xlocale 3
 118 for more information.
 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 strtod_l 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 BUGS
 175 These routines do not recognize the C99 ``NaN(...)'' syntax.
 176 .Sh AUTHORS
 177 The author of this software is
 178 .An David M. Gay .
 179 .Pp
 180 .Bd -literal
 181 Copyright (c) 1998 by Lucent Technologies
 182 All Rights Reserved
 183
 184 Permission to use, copy, modify, and distribute this software and
 185 its documentation for any purpose and without fee is hereby
 186 granted, provided that the above copyright notice appear in all
 187 copies and that both that the copyright notice and this
 188 permission notice and warranty disclaimer appear in supporting
 189 documentation, and that the name of Lucent or any of its entities
 190 not be used in advertising or publicity pertaining to
 191 distribution of the software without specific, written prior
 192 permission.
 193
 194 LUCENT DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
 195 INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS.
 196 IN NO EVENT SHALL LUCENT OR ANY OF ITS ENTITIES BE LIABLE FOR ANY
 197 SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 198 WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER
 199 IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
 200 ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF
 201 THIS SOFTWARE.
 202 .Ed