STRTOD(3) NEWLIB STRTOD(3)NAME
2.34 `strtod', `strtof'--string to double or float
SYNOPSIS
#include <stdlib.h>
double strtod(const char *STR, char **TAIL);
float strtof(const char *STR, char **TAIL);
double _strtod_r(void *REENT,
const char *STR, char **TAIL);
DESCRIPTION
The function `strtod' parses the character string STR, producing a sub‐
string which can be converted to a double value. The substring con‐
verted is the longest initial subsequence of STR, beginning with the
first non-whitespace character, that has one of these formats:
[+|-]DIGITS[.[DIGITS]][(e|E)[+|-]DIGITS]
[+|-].DIGITS[(e|E)[+|-]DIGITS]
[+|-](i|I)(n|N)(f|F)[(i|I)(n|N)(i|I)(t|T)(y|Y)]
[+|-](n|N)(a|A)(n|N)[<(>[HEXDIGITS]<)>]
[+|-]0(x|X)HEXDIGITS[.[HEXDIGITS]][(p|P)[+|-]DIGITS]
[+|-]0(x|X).HEXDIGITS[(p|P)[+|-]DIGITS]
The substring contains no characters if STR is empty, consists
entirely of whitespace, or if the first non-whitespace character is
something other than `+', `-', `.', or a digit, and cannot be parsed as
infinity or NaN. If the platform does not support NaN, then NaN is
treated as an empty substring. If the substring is empty, no conver‐
sion is done, and the value of STR is stored in `*TAIL'. Otherwise,
the substring is converted, and a pointer to the final string (which
will contain at least the terminating null character of STR) is stored
in `*TAIL'. If you want no assignment to `*TAIL', pass a null pointer
as TAIL. `strtof' is identical to `strtod' except for its return type.
This implementation returns the nearest machine number to the input
decimal string. Ties are broken by using the IEEE round-even rule.
However, `strtof' is currently subject to double rounding errors.
The alternate function `_strtod_r' is a reentrant version. The
extra argument REENT is a pointer to a reentrancy structure.
RETURNS
`strtod' returns the converted substring value, if any. If no conver‐
sion could be performed, 0 is returned. If the correct value is out of
the range of representable values, plus or minus `HUGE_VAL' is
returned, and `ERANGE' is stored in errno. If the correct value would
cause underflow, 0 is returned and `ERANGE' is stored in errno.
Supporting OS subroutines required: `close', `fstat', `isatty',
`lseek', `read', `sbrk', `write'.
SEE ALSOstrtod is part of the library. The full documentation for is main‐
tained as a Texinfo manual. If info and are properly installed at your
site, the command
info
will give you access to the complete manual.
NEWLIB April 2010 STRTOD(3)
