STRTOD(3)                BSD Library Functions Manual                STRTOD(3)

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

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <stdlib.h>

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

     float
     strtof(const char *restrict nptr, char **restrict endptr);

     long double
     strtold(const char *restrict nptr, char **restrict endptr);

DESCRIPTION
     These conversion 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 string is an optional plus (``+'') or minus
     (``-'') sign, followed by either:

     o   a decimal significand, consisting of a sequence of decimal digits
         (optionally containing a decimal-point character) or

     o   a hexadecimal significand, consisting of a ``0X'' or ``0x'' followed
         by a sequence of hexadecimal digits (optionally containing a decimal-
         point character).

     In both cases, the significand may be optionally followed by an exponent.
     An exponent consists of an ``E'' or ``e'' (for decimal constants) or a
     ``P'' or ``p'' (for hexadecimal constants), followed by an optional plus
     or minus sign, followed by a sequence of decimal digits.  For decimal
     constants, the exponent indicates the power of 10 by which the signifi-
     cand should be scaled.  For hexadecimal constants, the scaling is instead
     done by powers of 2.

     Alternatively, if the portion of the string following the optional plus
     or minus sign begins with ``INFINITY'' or ``NAN'', ignoring case, it is
     interpreted as an infinity or a quiet NaN, respectively.  The syntax
     ``NAN(s)'', where s is an alphanumeric string, produces the same value as
     the call nan("s") (respectively, nanf("s") and nanl("s").)

     In any of the above cases, leading white-space characters in the string
     (as defined by the isspace(3) function) are skipped.  The decimal point
     character is defined in the program's locale (category LC_NUMERIC).

     Extended locale versions of these functions are documented in
     strtod_l(3).  See xlocale(3) for more information.

RETURN VALUES
     The strtod(), strtof(), and strtold() functions return the converted
     value, if any.

     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,
     HUGE_VALF, or HUGE_VALL is returned (according to the sign and type of
     the return 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), nan(3), strtod_l(3), strtol(3), strtoul(3),
     wcstod(3)

STANDARDS
     The strtod() function conforms to ISO/IEC 9899:1999 (``ISO C99'').

AUTHORS
     The author of this software is David M. Gay.

     Copyright (c) 1998 by Lucent Technologies
     All Rights Reserved

     Permission to use, copy, modify, and distribute this software and
     its documentation for any purpose and without fee is hereby
     granted, provided that the above copyright notice appear in all
     copies and that both that the copyright notice and this
     permission notice and warranty disclaimer appear in supporting
     documentation, and that the name of Lucent or any of its entities
     not be used in advertising or publicity pertaining to
     distribution of the software without specific, written prior
     permission.

     LUCENT DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
     INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS.
     IN NO EVENT SHALL LUCENT OR ANY OF ITS ENTITIES BE LIABLE FOR ANY
     SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
     WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER
     IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
     ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF
     THIS SOFTWARE.

BSD                              March 2, 2003                             BSD