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strtod
Converts a string to a double-precision, floating-point number.
Syntax
#include <stdlib.h>
double strtod (const char *str, char **ptr);
Parameters
str A pointer to a character string to be converted.
ptr If ptr is not NULL, a pointer to the character terminating
the scan is stored in the object pointed to by ptr.
Return Values
x A double-precision floating-point number resulting from the
successful conversion of the string.
0 Indicates failure unless the value pointed to by str is
zero.
* If *ptr is set to str, no number can be formed.
* If *ptr is greater than str, the value pointed to by
*str is zero.
* If errno is set to ERANGE, the correct value of the
conversion would cause an underflow.
+-HUGE_VAL The conversion would cause an overflow; errno is set to
ERANGE.
Description
The strtod() function returns as a double-precision, floating-point
number the value represented by the character string pointed to by str.
The string is scanned up to the first unrecognizable character.
The string must contain a decimal constant or a floating-point constant
that may optionally be preceded by white space. The complete string may
contain the following in the order listed:
1. Optional white-space characters (as defined by isspace() ).
2. Optional sign.
3. Required string of digits, optionally containing a decimal point.
4. Optional e or E.
5. Optional sign or space.
6. Integer.
See Also
strtol(), strtoul(), atof(), ANSI C 4.10.1.4