NAME

strtod, atof − convert string to double-precision number

SYNOPSIS

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

double atof (str)
char ∗str;

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 decimal point, then an optional e or E followed by an optional sign or space, followed by an integer. 

If the value of ptr is not (char ∗∗)NULL, a pointer to the character terminating the scan is returned in the location pointed to by ptr. If no number can be formed, ∗ptr is set to str, and zero is returned.

atof(str) is equivalent to strtod(str, (char ∗∗)NULL).

SEE ALSO

ctype(3C), scanf(3S), strtol(3C)

DIAGNOSTICS

If the correct value would cause overflow, ±HUGE (as defined in <math.h>) is returned (according to the sign of the value), and errno is set to ERANGE∗S. 
If the correct value would cause underflow, zero is returned and errno is set to ERANGE. 

September 02, 1992