stdlib/FreeBSD/strtod.3

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  36 .\"     @(#)strtod.3    8.1 (Berkeley) 6/4/93
  37 .\" $FreeBSD: src/lib/libc/stdlib/strtod.3,v 1.18 2003/03/12 20:31:05 das 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 .Fn strtod "const char * restrict nptr" "char ** restrict endptr"
  53 .Ft float
  54 .Fn strtof "const char * restrict nptr" "char ** restrict endptr"
  55 .Ft long double
  56 .Fn strtold "const char * restrict nptr" "char ** restrict endptr"
  57 .Sh DESCRIPTION
  58 These conversion
  59 functions convert the initial portion of the string
  60 pointed to by
  61 .Fa nptr
  62 to
  63 .Vt double ,
  64 .Vt float ,
  65 and
  66 .Vt long double
  67 representation, respectively.
  68 .Pp
  69 The expected form of the string is an optional plus (``+'') or minus
  70 sign (``\-'') followed by either:
  71 .Bl -bullet
  72 .It
  73 a decimal significand consisting of a sequence of decimal digits
  74 optionally containing a decimal-point character, or
  75 .It
  76 a hexadecimal significand consisting of a ``0X'' or ``0x'' followed
  77 by a sequence of hexadecimal digits optionally containing a
  78 decimal-point character.
  79 .El
  80 .Pp
  81 In both cases, the significand may be optionally followed by an
  82 exponent.
  83 An exponent consists of an ``E'' or ``e'' (for decimal
  84 constants) or a ``P'' or ``p'' (for hexadecimal constants),
  85 followed by an optional plus or minus sign, followed by a
  86 sequence of decimal digits.
  87 For decimal constants, the exponent indicates the power of 10 by
  88 which the significand should be scaled.
  89 For hexadecimal constants, the scaling is instead done by powers
  90 of 2.
  91 .Pp
  92 Alternatively, if the portion of the string following the optional
  93 plus or minus sign begins with ``INFINITY'' or ``NAN'', ignoring
  94 case, it is interpreted as an infinity or a quiet NaN, respectively.
  95 .Pp
  96 In any of the above cases, leading white-space characters in the
  97 string (as defined by the
  98 .Xr isspace 3
  99 function) are skipped.
 100 The decimal point
 101 character is defined in the program's locale (category
 102 .Dv LC_NUMERIC ) .
 103 .Sh RETURN VALUES
 104 The
 105 .Fn strtod ,
 106 .Fn strtof ,
 107 and
 108 .Fn strtold
 109 functions return the converted value, if any.
 110 .Pp
 111 If
 112 .Fa endptr
 113 is not
 114 .Dv NULL ,
 115 a pointer to the character after the last character used
 116 in the conversion is stored in the location referenced by
 117 .Fa endptr .
 118 .Pp
 119 If no conversion is performed, zero is returned and the value of
 120 .Fa nptr
 121 is stored in the location referenced by
 122 .Fa endptr .
 123 .Pp
 124 If the correct value would cause overflow, plus or minus
 125 .Dv HUGE_VAL ,
 126 .Dv HUGE_VALF ,
 127 or
 128 .Dv HUGE_VALL
 129 is returned (according to the sign and type of the return value), and
 130 .Er ERANGE
 131 is stored in
 132 .Va errno .
 133 If the correct value would cause underflow, zero is
 134 returned and
 135 .Er ERANGE
 136 is stored in
 137 .Va errno .
 138 .Sh ERRORS
 139 .Bl -tag -width Er
 140 .It Bq Er ERANGE
 141 Overflow or underflow occurred.
 142 .El
 143 .Sh SEE ALSO
 144 .Xr atof 3 ,
 145 .Xr atoi 3 ,
 146 .Xr atol 3 ,
 147 .Xr strtol 3 ,
 148 .Xr strtoul 3 ,
 149 .Xr wcstod 3
 150 .Sh STANDARDS
 151 The
 152 .Fn strtod
 153 function
 154 conforms to
 155 .St -isoC-99 ,
 156 with the exception of the bug noted below.
 157 .Sh BUGS
 158 These routines do not recognize the C99 ``NaN(...)'' syntax.
 159 .Sh AUTHORS
 160 The author of this software is
 161 .An David M. Gay .
 162 .Pp
 163 Copyright (c) 1998 by Lucent Technologies
 164 .br
 165 All Rights Reserved
 166 .Pp
 167 Permission to use, copy, modify, and distribute this software and
 168 its documentation for any purpose and without fee is hereby
 169 granted, provided that the above copyright notice appear in all
 170 copies and that both that the copyright notice and this
 171 permission notice and warranty disclaimer appear in supporting
 172 documentation, and that the name of Lucent or any of its entities
 173 not be used in advertising or publicity pertaining to
 174 distribution of the software without specific, written prior
 175 permission.
 176 .Pp
 177 LUCENT DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
 178 INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS.
 179 IN NO EVENT SHALL LUCENT OR ANY OF ITS ENTITIES BE LIABLE FOR ANY
 180 SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 181 WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER
 182 IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
 183 ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF
 184 THIS SOFTWARE.