STRTOD(3)

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

LIBRARY
libc

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:

•   a decimal significand consisting of a sequence of decimal digits optionally containing a decimal-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 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 isoC-99, 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.