strtod, strtodf---string to double or float
#include <stdlib.h>
double strtod(const char *str, char **tail);
float strtodf(const char *str, char **tail);
double _strtod_r(void *reent,
const char *str, char **tail);
Descriptionstrtod parses the character string str,
producing a substring which can be converted to a double
value. The substring converted is the longest initial
subsequence of str, beginning with the first
non-whitespace character, that has the format:
[+|-]digits[.][digits][(e|E)[+|-]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. If the substring is empty, no conversion 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.
strtodf 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.
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 conversion 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.