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LETTERatofULETTER Converts an ASCII string to a floating-point number.

Overview
#include <stdlib.h>

x = atof(s);

double x; // floating-point result
const char *s; // source string pointer

Portability
ANSI

Description
This function converts an ASCII string to a double-precision floating-point number. Calling "atof" equals "strtod(string, 0)".

The input string is assumed to have the following format:
[ws][sign]digits[.][digits][e|E[sign]digits]
where ws stands for any number of whitespaces (plain spaces and tabs), sign is either '+' or '-' and digits means a sequence of numbers between 0 and 9. All elements within "[]" brackets are optional. The following string is valid for atof:
+123.456e-78

Returns
This function returns the double-precision equivalent of the ASCII string passed to it. If an overflow occurs it will return plus or minus HUGE_VAL and errno will contain ERANGE.

See also
atoi , atol , strtod

Example
#include <stdio.h>
#include <math.h>

void main(void)
{ char buff[80];
double d;

while(1)
{ printf("\nPlease enter a number: ");
if(fgets(buff, sizeof(buff), stdin) == NULL)
{
break;
} if(buff[0] == '\0')
{
break;
} d = atof(buff);
printf("%e\n",d);
} printf("\n");
}