HP-UX Reference (11i v2 03/08) - 3 Library Functions N-Z (vol 7)

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strtod(3C) strtod(3C)
NAME
strtod, strtof, strtold, strtow, strtoq, atof - convert string to floating-point number
SYNOPSIS
#include <stdlib.h>
double strtod(const char *str, char **ptr);
long double strtold(const char *str, char **ptr);
double atof(const char *str);
Itanium(R)-based System Only
float strtof(const char *str, char **ptr);
extended strtow(const char *str, char **ptr);
quad strtoq(const char *str, char **ptr);
DESCRIPTION
strtod() returns, as a double-precision floating-point number, the value represented by the character
string pointed to by str. The string is scanned (leading white-space characters as defined by
isspace() in ctype (3C) are ignored) up to the first unrecognized character. If no conversion can take
place, zero is returned.
strtod() 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
e or
E, fol-
lowed by an optional sign or space, followed by an integer
4. One of
INF or INFINITY, ignoring case
5. NAN, ignoring case
6. For Itanium-based system only:
0x or 0X, then a nonempty sequence of hexadecimal digits
optionally containing a radix character, then a
p or P, followed by an optional sign or space,
followed by a decimal integer
The radix character is determined by the loaded NLS environment (see setlocale (3C)). If
setlocale()
has not been called successfully, the default NLS environment, "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 following the
p or P is interpreted as the
power of 2 by which the significand part is to be scaled.
If the value of ptr is not
(char **)NULL, the variable to which it points is set to point at the character
after the last number, if any, that was recognized. If no number can be formed, *ptr is set to str, and
zero is returned.
atof(str) is equivalent to strtod (str, (char **)NULL).
strtold() is a long double version of strtod(); it returns a long double result. For PA-
RISC and for Itanium-based systems, if the user has defined _LONG_DOUBLE_STRUCT
, the result type
is declared as a
struct, instead of as a long double. The declaration with a struct is obsolescent.
Itanium-based System Only
strtof() is a float version of strtod(); it returns a float result.
strtow() is an extended version of strtod(); it returns an extended result.
strtoq() is equivalent to strtold().
EXTERNAL INFLUENCES
Locale
The
LC_NUMERIC category determines the value of the radix character within the currently loaded NLS
environment.
HP-UX 11i Version 2: August 2003 − 1 − Hewlett-Packard Company Section 3−−1005