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STRTOD(3)             DragonFly Library Functions Manual             STRTOD(3)


NAME

     strtod, strtod_l, strtof, strtof_l, strtold, strtold_l -- 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);

     #include <xlocale.h>

     double
     strtod_l(const char * restrict nptr, char ** restrict endptr,
         locale_t locale);

     float
     strtof_l(const char * restrict nptr, char ** restrict endptr,
         locale_t locale);

     long double
     strtold_l(const char * restrict nptr, char ** restrict endptr,
         locale_t locale);


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
     significand 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.

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

     The strtod_l(), strtof_l(), and strtold_l() functions take an explicit
     locale argument, whereas the strtod(), strtof(), and strtold() functions
     use the current global or per-thread locale.


RETURN VALUES

     The strtod(), strtod_l(), strtof(), strtof_l(), strtold(), and
     strtold_l() 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, 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), strtol(3), strtoul(3), wcstod(3), xlocale(3)


STANDARDS

     The strtod() function conforms to ISO/IEC 9899:1999 (``ISO C99''), with
     the exception of the bug noted below.


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.


BUGS

     These routines do not recognize the C99 ``NaN(...)'' syntax.

DragonFly 3.7                  December 25, 2013                 DragonFly 3.7

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