NAME

strtod, atof, nl_strtod, nl_atof − convert string to double-precision number

SYNOPSIS

double strtod (str, ptr)
char ∗str, ∗∗ptr;

double atof (str)
char ∗str;

double nl_strtod (str, ptr, langid)
char ∗str, ∗∗ptr;
int langid;

double nl_atof (str, langid)
char ∗str;
inl langid;

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 up to the first unrecognized character.

Strtod recognizes an optional string of “white-space” characters (as defined by isspace in ctype(3C)), then an optional sign, then a string of digits optionally containing a radix character, then an optional e or E followed by an optional sign or space, followed by an integer.  The radix character is determined by the loaded NLS environment (see nl_init(3C)). If nl_init has not been called successfully, the default NLS environment, ­"n-computer" (see langid(5)), is used.  The default environment specifies a period (.) as the radix character.

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). 

Nl_strtod and nl_atof are similar to the above routines, but first call langinit (see nl_init(3C)) to load the NLS environment specified by langid.

DIAGNOSTICS

If the correct value would cause overflow, ±HUGE is returned (according to the sign of the value), and errno is set to ERANGE.  HUGE_VAL may be used instead of HUGE. 

If the correct value would cause underflow, zero is returned and errno is set to ERANGE. 

WARNINGS

Nl_strtod and nl_atof are provided for historical reasons only.  Their use is not recommended.  Use strtod and atof instead. 

AUTHOR

Strtod was developed by AT&T and HP. 

SEE ALSO

ctype(3C), nl_init(3C), scanf(3S), strtol(3C), hpnls(5), langid(5). 

INTERNATIONAL SUPPORT

8-bit data. 

Hewlett-Packard Company  —  May 11, 2021