strtod(3) - NetBSD Manual Pages

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STRTOD(3)               NetBSD Library Functions Manual              STRTOD(3)


NAME

     strtod -- convert ASCII string to double


LIBRARY

     Standard C Library (libc, -lc)


SYNOPSIS

     #include <stdlib.h>

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


DESCRIPTION

     The strtod() function converts the initial portion of the string pointed
     to by nptr to double representation.

     The expected form of the string is an optional plus (``+'') or minus sign
     (``-'') followed by one of the following:

     -   a sequence of digits optionally containing a decimal-point character,
         optionally followed by an exponent.  An exponent consists of an ``E''
         or ``e'', followed by an optional plus or minus sign, followed by a
         sequence of digits.

     -   one of INF or INFINITY, ignoring case.

     -   one of NAN or NAN(n-char-sequence-opt), ignoring case.  This imple-
         mentation currently does not interpret such a sequence.

     Leading white-space characters in the string (as defined by the
     isspace(3) function) are skipped.


RETURN VALUES

     The strtod() function returns the converted value, if any.

     A character sequence INF or INFINITY is converted to infinity, if sup-
     ported, else to the largest finite floating-point number representable on
     the machine (i.e., VAX).

     A character sequence NAN or NAN(n-char-sequence-opt) is converted to a
     quiet NaN, if supported, else remains unrecognized (i.e., VAX).

     If endptr is not NULL, a pointer to the character after the last charac-
     ter 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 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.


SEE ALSO

     atof(3), atoi(3), atol(3), math(3), strtol(3), strtoul(3)


STANDARDS

     The strtod() function conforms to ANSI X3.159-1989 (``ANSI C89'').

NetBSD 3.1.1                    April 15, 2005                    NetBSD 3.1.1