strtod(3C)strtod(3C)NAMEstrtod(), strtof(), strtold(), strtow(), strtoq(), atof() - convert
string to floating-point number
SYNOPSISItanium(R)-based Systems Only
DESCRIPTION
returns, as a double-precision floating-point number, the value repre‐
sented by the character string pointed to by str. The string is
scanned (leading white-space characters as defined by in ctype(3C) are
ignored) up to the first unrecognized character. If no conversion can
take place, zero is returned.
recognizes characters in the following sequence:
1. An optional string of white space characters which are
ignored
2. An optional sign
and one of the following:
3. A string of digits optionally containing a radix character,
followed by an optional or followed by an optional sign or
space, followed by an integer
4. One of or ignoring case
5. ignoring case
6. For Itanium-based system only: or then a nonempty sequence
of hexadecimal digits optionally containing a radix charac‐
ter, then a or followed by an optional sign or space, fol‐
lowed by a decimal integer
The radix character is determined by the loaded environment (see setlo‐
cale(3C)). If has not been called successfully, the default environ‐
ment, "C", is used (see lang(5)). The default environment specifies a
period as the radix character.
In the hexadecimal form, the optionally signed decimal integer follow‐
ing the or is interpreted as the power of 2 by which the significant
part is to be scaled.
If the value of ptr is not the variable to which it points is set to
point at the character after the last number, if any, that was recog‐
nized. If no number can be formed, is set to str, and zero is
returned.
is equivalent to
is a version of it returns a result. For PA-RISC and for Itanium-based
systems, if the user has defined the result type is declared as a
instead of as a The declaration with a is obsolescent.
Itanium-based Systems Only
is a version of it returns a result.
is an version of it returns an result.
is equivalent to
EXTERNAL INFLUENCES
Environment Variables
determines the value of the radix character within the currently loaded
environment.
APPLICATION USAGE
To use (for Itanium-based systems) or compile with the option.
RETURN VALUE
If the correct value would cause overflow, returns (equal to according
to the sign of the value, and sets to
If the correct value would be nonzero but too small in magnitude to
represent as a nonzero then returns zero and sets to For Itanium-based
system, also sets to whenever the conversion of its input parameter
character string to raises the underflow exception.
When the input parameter character string for after the optional white
space and sign, is either (case insensitive) or (case insensitive) will
return according to the sign indicated by the character string.
When the input parameter character string for after the optional white
space and sign, is (case insensitive), will return a quiet NaN.
On Itanium-based systems, these functions round correctly for hexadeci‐
mal input strings, and round correctly for up to 36 significant decimal
digits, according to the specification in ISO/IEC C99.
SEE ALSOctype(3C), setlocale(3C), scanf(3S), strtol(3C), lang(5),
thread_safety(5).
STANDARDS CONFORMANCEstrtod(3C)