strtod, strtof, strtold - convert string to double-precision number

Definition	#include <stdlib.h> double strtod(const char *s, char **endptr); float strtof(const char *s, char **endptr); long double strtold(const char *s, char **endptr);
Description	These functions convert the string to which s points into a floating-point number of type double. The string to be converted may be structured as follows: [{ tab |'BLANK'}...][+|-][ digit ...][.][ digit ...][{E|e}[+|-] digit ...] or [{ tab |'BLANK'}...][+|-]0{X|x}[ hexdigit ...][.][ hexdigit ...][{P|p}[+|-] digit ...] Any white-space character may be used for tab (see definition under isspace()). strtod() also recognizes strings that start with a digit but end with some other character. In such cases, strtod() first truncates the numeric part and converts it to a floating-point value. strtod() returns a pointer (*endptr) to the first non-convertible character in string s via the second argument endptr of type char **, but only if endptr is not passed as a null pointer. If endptr is a null pointer, strtod() is executed like the atof() function: atof(s) is equivalent to strtod(s, (char **)NULL) and strtod(s, NULL). If endptr is not a null pointer, a pointer (*endptr) to the first character in s that completes the conversion is returned. If absolutely no conversion is possible, *endptr will be set to the start address of string s.
Return val.	Floating-point number of type double, float or long double
		for strings which are structured as described above and represent a numeric value within the permissible floating-point range.
	0	for strings that do not conform to the syntax described above or do not begin with convertible characters.
	+/-HUGE_VAL +/-HUGE_VALF +/-HUGE_VALL	depending on the function type and the sign of x, for strings whose numeric value lies outside the permissible floating-point range. errno is set to indicate the error.
Errors	strtod() will fail if:
	ERANGE	The return value causes an overflow or underflow
	EINVAL	No conversion could be performed.
Notes	The radix character in the string to be converted is determined by LC_NUMERIC category of the locale. The default is a period.
See also	atof(), atoi(), atol(), isspace(), strtol(), strtoul(), stdlib.h.