strtod, strtof, strtold — convert ASCII string to floating-point number
||const char *nptr,|
||const char *nptr,|
||const char *nptr,|
strtold() functions convert the initial
portion of the string pointed to by
nptr to double, float, and
long double representation,
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-number).
A decimal number consists of a nonempty sequence of decimal digits possibly 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 nonempty 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 nonempty 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.
NAN is "NAN" (disregarding
case) optionally followed by a string,
specifies in an implementation-dependent way the type of NAN
These functions return the converted value, if any.
endptr is not
NULL, a pointer to the character after the last character
used in the conversion is stored in the location referenced
If no conversion is performed, zero is returned and
null) the value of
nptr is stored in the location
If the correct value would cause overflow, plus or minus
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
For an explanation of the terms used in this section, see attributes(7).
||Thread safety||MT-Safe locale|
Since 0 can legitimately be returned on both success and
failure, the calling program should set
errno to 0 before the call, and then
determine if an error occurred by checking whether
errno has a nonzero value after
In the glibc implementation, the
optionally follows "NAN" is interpreted as an integer number
(with an optional '0' or '0x' prefix to select base 8 or 16)
that is to be placed in the mantissa component of the
See the example on the strtol(3) manual page; the use of the functions described in this manual page is similar.
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(#)strtod.3 5.3 (Berkeley) 6/29/91
Modified Sun Aug 21 17:16:22 1994 by Rik Faith (faithcs.unc.edu)
Modified Sat May 04 19:34:31 MET DST 1996 by Michael Haardt
Added strof, strtold, aeb, 2001-06-07