STRTOD(3) Library functions STRTOD(3)
strtod, strtof, strtold - convert ASCII string to floating point number
double strtod(const char *nptr, char **endptr);
float strtof(const char *nptr, char **endptr);
long double strtold(const char *nptr, char **endptr);
The strtod, strtof, and strtold functions convert the initial portion
of the string pointed to by nptr to double, float, and long double rep-
The expected form of the (initial portion of the) string is optional
leading white space as recognized by isspace(3), an optional plus
(``+'') or minus sign (``-'') and then either (i) a decimal number, or
(ii) a hexadecimal number, or (iii) an infinity, or (iv) a NAN (not-a-
A decimal number consists of a nonempty sequence of decimal digits pos-
sibly containing a radix character (decimal point, locale dependent,
usually ``.''), optionally followed by a decimal exponent. A decimal
exponent consists of an ``E'' or ``e'', followed by an optional plus or
minus sign, followed by a non-empty sequence of decimal digits, and
indicates multiplication by a power of 10.
A hexadecimal number consists of a ``0x'' or ``0X'' followed by a
nonempty sequence of hexadecimal digits possibly containing a radix
character, optionally followed by a binary exponent. A binary exponent
consists of a ``P'' or ``p'', followed by an optional plus or minus
sign, followed by a non-empty sequence of decimal digits, and indicates
multiplication by a power of 2. At least one of radix character and
binary exponent must be present.
An infinity is either ``INF'' or ``INFINITY'', disregarding case.
A NAN is ``NAN'' (disregarding case) optionally followed by `(', a
sequence of characters, followed by ')'. The character string speci-
fies in an implementation-dependent way the type of NAN.
These functions return the converted value, if any.
If endptr is not NULL, a pointer to the character after the last char-
acter 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
(HUGE_VALF, HUGE_VALL) 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.
ANSI C describes strtod, C99 describes the other two functions.
atof(3), atoi(3), atol(3), strtol(3), strtoul(3)
Linux 2001-06-07 STRTOD(3)