STRTOD(3) | Library Functions Manual | STRTOD(3) |
strtod
, strtof
,
strtold
— convert ASCII
string to double, float or long double
#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);
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.
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.
ERANGE
]The strtod
() function conforms to
ANSI X3.159-1989 (“ANSI C89”).
The strtof
() and strtold
()
functions conform to ISO/IEC 9899:1999
(“ISO C99”).
On systems other than OpenBSD, the
LC_NUMERIC
locale(1) category can cause parsing
failures; see CAVEATS in setlocale(3)
for details.
January 16, 2019 | OpenBSD-current |