atof(3) 						     Library Functions Manual							   atof(3)

NAME

       atof, strtod, strtof, strtold - Converts a character string to a double-precision floating-point value

LIBRARY

       Standard C Library (libc.a)

SYNOPSIS

       #include <stdlib.h>

       double atof(
	   const char *nptr);

       double strtod(
	   const char *nptr,
	   char **endptr);

       float strtof(
	   const char *nptr,
	   char **endptr);

       long double strtold(
	   const char *nptr,
	   char **endptr);

PARAMETERS

       Points  to the character string to convert.  Specifies either a null value, a pointer to the character that ended the scan, or a pointer to
       a null value.

DESCRIPTION

       The atof() function converts, to a double floating-point value, the string pointed to by the nptr parameter - up  to  the  first  character
       that  is inconsistent with the format of a floating-point number.  Leading space characters are ignored. A call to this function is equiva-
       lent to a call to strtod(nptr, (char **) NULL), except for error handling. When the value cannot be represented, the result is undefined.

       The strtod(), strtof(), and strtold() functions convert the initial portion of the string pointed to  by  the  nptr  parameter  to  double,
       float,  and  long  double  representation, respectively.  First, the input string is decomposed into the following three parts: An initial,
       possibly empty, sequence of space characters (as specified by the isspace() function).  A subject sequence interpreted as a  floating-point
       constant.  A final string of one or more unrecognized characters, including the terminating null character of the input string.

       After  decomposition  of  the  string, the subject sequence is converted to a floating-point number and the resulting value is returned.  A
       subject sequence is defined as the longest initial subsequence of the input string, starting with the first non-space character, that is of
       the  expected form.  The expected form and order of the subject sequence is: An optional plus (+) or minus (-) sign.  A	sequence of digits
       optionally containing a radix character.  An optional exponent part. An exponent part consists of e or E, followed  by  an  optional  sign,
       which is followed by one or more decimal digits.

       The subject sequence contains no characters when the input string is empty or consists entirely of space characters, or when the first non-
       space character is other than a sign, a digit, or a radix character.

       For the strtod(), strtof(), and strtold() functions, when the value of the endptr parameter is not (char**) NULL, a pointer to the  charac-
       ter that terminated the scan is stored at *endptr.

       When a floating-point value cannot be formed, *endptr is set to nptr.

       The strings NaN ("not a number"), Inf, and Infinity (the case of the characters does not matter) are recognized as valid only when the pro-
       gram is compiled with the -ieee option.

NOTES

       The setlocale() function may affect the radix character used in the conversion result.  Full use

RETURN VALUES

       When the string is empty or begins with an unrecognized character, +0.0 is returned as the floating-point value.

       If the calling routine is compiled with IEEE floating point enabled (-ieee flag), errno will be set to ERANGE if the conversion	underflows
       to zero.  Similarly, if the value overflows, ERANGE will be set and a properly signed infinity will be returned.

       If  the calling routine is not compiled with IEEE floating point enabled, any underflow will cause errno to be set to ERANGE and a properly
       signed zero to be returned.  An overflow will cause errno to be set to ERANGE and will return a	properly  signed  DBL_MAX,  FLOAT_MAX,	or
       LDBL_MAX.

       Upon successful completion, all of the functions return the converted floating-point value.

ERRORS

       If  the	atof(), strtod(), strtof(), or strtold() function fails, errno may be set to the following value: The input string is out of range
       (that is, the subject sequence cannot be converted to a floating-point value without causing underflow or overflow).

RELATED INFORMATION

       Functions: atoi(3), scanf(3) delim off

																	   atof(3)