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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:

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

     •   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 significand should be scaled.  For hexadecimal con-stants, constants,
     stants, 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 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 refer-enced referenced
     enced 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

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