STRTOD(3)                               Library functions                               STRTOD(3)



NAME
       strtod, strtof, strtold - convert ASCII string to floating point number

SYNOPSIS
       #include 

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

DESCRIPTION
       The  strtod,  strtof,  and  strtold  functions  convert  the initial portion of the string
       pointed to by nptr to double, float, and long double representation, respectively.

       The expected form of the (initial portion of the) string is optional leading  white  space
       as  recognized  by  isspace(3),  an  optional  plus (''+'') or minus sign (''-'') and then
       either (i) a decimal number, or (ii) a hexadecimal number, or (iii) an infinity, or (iv) a
       NAN (not-a-number).

       A  decimal  number consists of a nonempty sequence of decimal digits possibly containing a
       radix character (decimal point, locale dependent, usually ''.''), optionally followed by a
       decimal  exponent.   A  decimal  exponent  consists  of  an ''E'' or ''e'', followed by an
       optional plus or minus sign, followed by a non-empty sequence of decimal digits, and indi-
       cates multiplication by a power of 10.

       A  hexadecimal  number  consists  of a ''0x'' or ''0X'' followed by a nonempty sequence of
       hexadecimal digits possibly containing a radix character, optionally followed by a  binary
       exponent.  A binary exponent consists of a ''P'' or ''p'', followed by an optional plus or
       minus sign, followed by a non-empty sequence of decimal digits, and indicates  multiplica-
       tion  by  a  power  of  2.   At  least  one of radix character and binary exponent must be
       present.

       An infinity is either ''INF'' or ''INFINITY'', disregarding case.

       A NAN is ''NAN'' (disregarding case) optionally followed by '(', a sequence of characters,
       followed  by  ')'.   The character string specifies in an implementation-dependent way the
       type of NAN.


RETURN VALUE
       These functions return the converted value, if any.

       If endptr is not NULL, a pointer to the character after the last  character  used  in  the
       conversion is stored in the location referenced by endptr.

       If  no  conversion  is  performed, zero is returned and the value of nptr is stored in the
       location referenced by endptr.

       If the correct value would cause overflow, plus or minus HUGE_VAL  (HUGE_VALF,  HUGE_VALL)
       is  returned  (according to the sign of the value), and ERANGE is stored in errno.  If the
       correct value would cause underflow, zero is returned and ERANGE is stored in errno.

ERRORS
       ERANGE Overflow or underflow occurred.

CONFORMING TO
       ANSI C describes strtod, C99 describes the other two functions.

SEE ALSO
       atof(3), atoi(3), atol(3), strtol(3), strtoul(3)



Linux                                       2001-06-07                                  STRTOD(3)