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:
oo a decimal significand, consisting of a sequence of decimal digits (optionally containing a decimal-point decimalpoint
point character) or
oo 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.
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), strtod_l(3), strtol(3), strtoul(3), wcstod(3)
STANDARDS
The strtod() function conforms to ISO/IEC 9899:1999 (``ISO C99''), with the exception of the bug noted
below.
BUGS
These routines do not recognize the C99 ``NaN(...)'' syntax.
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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