NAME
strtod, strtof,
strtold —
convert ASCII string to double, float
or long double
SYNOPSIS
#include
<stdlib.h>
double
strtod(const
char *nptr, char
**endptr);
float
strtof(const
char *nptr, char
**endptr);
long double
strtold(const
char *nptr, char
**endptr);
DESCRIPTION
The
strtod()
function converts the initial portion of the string pointed to by
nptr to double representation.
The
strtof()
function converts the initial portion of the string pointed to by
nptr to float representation.
The
strtold()
function converts the initial portion of the string pointed to by
nptr to long double
representation.
The expected form of the string is an optional plus
(‘+’) or minus sign
(‘-’) followed by 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.
Alternatively, if the portion of the string following the
optional plus or minus sign begins with “INF” or
“NAN”, ignoring case, it is interpreted as an infinity or a
quiet NaN, respectively. The syntax
“NAN(s)”, where s
is an alphanumeric string, produces the same value as the call
nan("s");
(respectively,
nanf("s");
and
nanl("s");).
In any of the above cases, leading whitespace characters in the string (as defined by the isspace(3) function) are skipped.
RETURN VALUES
The strtod(),
strtof() and strtold()
functions return the converted value, if any.
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
endptr.
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.
ERRORS
- [
ERANGE] - Overflow or underflow occurred.
SEE ALSO
STANDARDS
The strtod() function conforms to
ANSI X3.159-1989 (“ANSI C89”).
The strtof() and strtold()
functions conform to ISO/IEC 9899:1999
(“ISO C99”).
CAVEATS
On systems other than OpenBSD, the
LC_NUMERIC
locale(1) category can cause parsing failures; see CAVEATS in
setlocale(3) for details.