The function first discards as many whitespace characters as necessary until the first non-whitespace character is found. Then, starting from this character, takes as many characters as possible that are valid following a syntax resembling that of floating point literals, and interprets them as a numerical value. A pointer to the rest of the string after the last valid character is stored in the object pointed by endptr.
A valid floating point number for strtod is formed by a succession of:
- An optional plus or minus sign
- A sequence of digits, optionally containing a decimal-point character
- An optional exponent part, which itself consists on an 'e' or 'E' character followed by an optional sign and a sequence of digits.
If the first sequence of non-whitespace characters in str does not form a valid floating-point number as just defined, or if no such sequence exists because either str is empty or contains only whitespace characters, no conversion is performed.
- C string beginning with the representation of a floating-point number.
- Reference to an already allocated object of type char*, whose value is set by the function to the next character in str after the numerical value.
This parameter can also be a null pointer, in which case it is not used.
Return ValueOn success, the function returns the converted floating point number as a double value.
If no valid conversion could be performed, a zero value (0.0) is returned.
If the correct value is out of the range of representable values, a positive or negative HUGE_VAL is returned, and the global variable errno is set to ERANGE.
If the correct value would cause underflow, zero is returned and errno is set to ERANGE.
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|atof||Convert string to double (function)|
|strtol||Convert string to long integer (function)|
|strtoul||Convert string to unsigned long integer (function)|