IABSD.fr/src/lib/libc/stdlib/strtod.3

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• Author : schwarze
  Date : 2019-01-16 12:55:49
  Hash : a41d0f37
  Message : For all functions known to be infected by LC_NUMERIC, add short CAVEATS pointing to the new CAVEATS section in setlocale(3). Make those in wprintf(3) and wscanf(3) more concise since duplicate information is a bad idea. Incompleteness of information originally pointed out by millert@. OK millert@

• lib/libc/stdlib/strtod.3

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  .\"	$OpenBSD: strtod.3,v 1.22 2019/01/16 12:55:49 schwarze Exp $
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  .Dd $Mdocdate: January 16 2019 $
  .Dt STRTOD 3
  .Os
  .Sh NAME
  .Nm strtod ,
  .Nm strtof ,
  .Nm strtold
  .Nd convert ASCII string to double, float or long double
  .Sh SYNOPSIS
  .In stdlib.h
  .Ft double
  .Fn strtod "const char *nptr" "char **endptr"
  .Pp
  .Ft float
  .Fn strtof "const char *nptr" "char **endptr"
  .Pp
  .Ft long double
  .Fn strtold "const char *nptr" "char **endptr"
  .Sh DESCRIPTION
  The
  .Fn strtod
  function converts the initial portion of the string pointed to by
  .Fa nptr
  to
  .Li double
  representation.
  The
  .Fn strtof
  function converts the initial portion of the string pointed to by
  .Fa nptr
  to
  .Li float
  representation.
  The
  .Fn strtold
  function converts the initial portion of the string pointed to by
  .Fa nptr
  to
  .Li long double
  representation.
  .Pp
  The expected form of the string is an optional plus
  .Pq Ql +
  or minus sign
  .Pq Ql -
  followed by a sequence of digits optionally containing
  a decimal-point character, optionally followed by an exponent.
  An exponent consists of an
  .Sq E
  or
  .Sq e ,
  followed by an optional plus or minus sign, followed by a sequence of digits.
  .Pp
  Alternatively, if the portion of the string following the optional
  plus or minus sign begins with
  .Dq INF
  or
  .Dq NAN ,
  ignoring case, it is interpreted as an infinity or a quiet \*(Na,
  respectively.
  The syntax
  .Dq NAN Ns Pq Ar s ,
  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 whitespace characters in the
  string (as defined by the
  .Xr isspace 3
  function) are skipped.
  .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
  is returned (according to the sign of the 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 strtol 3 ,
  .Xr strtoul 3
  .Sh STANDARDS
  The
  .Fn strtod
  function conforms to
  .St -ansiC-89 .
  The
  .Fn strtof
  and
  .Fn strtold
  functions conform to
  .St -isoC-99 .
  .Sh CAVEATS
  On systems other than
  .Ox ,
  the
  .Dv LC_NUMERIC
  .Xr locale 1
  category can cause parsing failures; see CAVEATS in
  .Xr setlocale 3
  for details.