STRTOD(D)               Library functions               STRTOD(D)



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

SYNOPSIS
       #include <stdlib.h>

       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 ini-
       tial  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 is-
       space(e), an optional plus (``+'') or minus  sign  (``-'')
       and  then either (i) a decimal number, or (ii) a hexadeci-
       mal number, or (iii) an infinity, or (iv)  a  NAN  (not-a-
       number).

       A  decimal number consists of a nonempty sequence of deci-
       mal digits possibly containing a radix character  (decimal
       point,  locale  dependent, usually ``.''), optionally fol-
       lowed 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 indicates multiplication by a power of 10.

       A  hexadecimal  number consists of a ``0x'' or ``0X'' fol-
       lowed by a nonempty sequence of hexadecimal digits  possi-
       bly 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, fol-
       lowed by a non-empty sequence of decimal digits, and indi-
       cates  multiplication  by  a  power of 2.  At least one of
       radix character and binary exponent must be present.

       An infinity is either ``INF'' or ``INFINITY'',  disregard-
       ing 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 func-
       tions.

SEE ALSO
       atof(f), atoi(i), atol(l), strtol(l), strtoul(l)



Linux                       2001-06-07                  STRTOD(D)