strtod - convert ASCII string to double
Standard C Library (libc, -lc)
strtod(const char * restrict nptr, char ** restrict endptr);
The strtod() function converts the initial portion of the string pointed
to by nptr to double representation.
The expected form of the string is an optional plus (``+'') or minus sign
(``-'') followed by one of the following:
- a sequence of digits optionally containing a decimal-point character,
optionally followed by an exponent. An exponent consists of an ``E''
or ``e'', followed by an optional plus or minus sign, followed by a
sequence of digits.
- one of INF or INFINITY, ignoring case.
- one of NAN or NAN(n-char-sequence-opt), ignoring case. This implementation
currently does not interpret such a sequence.
Leading white-space characters in the string (as defined by the
isspace(3) function) are skipped.
The strtod() function returns the converted value, if any.
A character sequence INF or INFINITY is converted to infinity, if supported,
else to the largest finite floating-point number representable on
the machine (i.e., VAX).
A character sequence NAN or NAN(n-char-sequence-opt) is converted to a
quiet NaN, if supported, else to a ``reserved operand'' for that machine
If endptr is not NULL, a pointer to the character after the last character
used in the conversion is stored in the location referenced by
If no conversion is performed, zero is returned and the value of nptr is
stored in the location referenced by endptr.
If the correct value would cause overflow, plus or minus HUGE_VAL is
returned (according to the sign of the value), and ERANGE is stored in
errno. If the correct value would cause underflow, zero is returned and
ERANGE is stored in errno.
[ERANGE] Overflow or underflow occurred.
atof(3), atoi(3), atol(3), math(3), strtol(3), strtoul(3)
The strtod() function conforms to ANSI X3.159-1989 (``ANSI C'').
BSD January 28, 2002 BSD
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