199 lines
5.9 KiB
Groff
199 lines
5.9 KiB
Groff
.\" Copyright (c) 1990, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" This code is derived from software contributed to Berkeley by
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.\" the American National Standards Committee X3, on Information
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.\" Processing Systems.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)strtod.3 8.1 (Berkeley) 6/4/93
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.\" $FreeBSD$
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.\"
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.Dd May 11, 2010
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.Dt STRTOD 3
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.Os
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.Sh NAME
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.Nm strtod , strtof , strtold
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.Nd convert
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.Tn ASCII
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string to floating point
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In stdlib.h
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.Ft double
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.Fn strtod "const char * restrict nptr" "char ** restrict endptr"
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.Ft float
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.Fn strtof "const char * restrict nptr" "char ** restrict endptr"
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.Ft "long double"
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.Fn strtold "const char * restrict nptr" "char ** restrict endptr"
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.Sh DESCRIPTION
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These conversion
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functions convert the initial portion of the string
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pointed to by
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.Fa nptr
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to
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.Vt double ,
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.Vt float ,
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and
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.Vt "long double"
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representation, respectively.
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.Pp
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The expected form of the string is an optional plus (``+'') or minus
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sign (``\-'') followed by either:
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.Bl -bullet
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.It
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a decimal significand consisting of a sequence of decimal digits
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optionally containing a decimal-point character, or
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.It
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a hexadecimal significand consisting of a ``0X'' or ``0x'' followed
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by a sequence of hexadecimal digits optionally containing a
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decimal-point character.
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.El
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.Pp
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In both cases, the significand may be optionally followed by an
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exponent.
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An exponent consists of an ``E'' or ``e'' (for decimal
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constants) or a ``P'' or ``p'' (for hexadecimal constants),
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followed by an optional plus or minus sign, followed by a
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sequence of decimal digits.
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For decimal constants, the exponent indicates the power of 10 by
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which the significand should be scaled.
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For hexadecimal constants, the scaling is instead done by powers
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of 2.
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.Pp
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Alternatively, if the portion of the string following the optional
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plus or minus sign begins with
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.Dq INFINITY
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or
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.Dq NAN ,
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ignoring case, it is interpreted as an infinity or a quiet \*(Na,
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respectively.
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The syntax
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.Dq Xo Pf NAN( Ar "s" ) Xc ,
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where
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.Ar s
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is an alphanumeric string, produces the same value as the call
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.Fo nan
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.Qq Ar s Ns
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.Fc
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(respectively,
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.Fo nanf
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.Qq Ar s Ns
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.Fc
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and
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.Fo nanl
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.Qq Ar s Ns
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.Fc . )
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.Pp
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In any of the above cases, leading white-space characters in the
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string (as defined by the
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.Xr isspace 3
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function) are skipped.
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The decimal point
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character is defined in the program's locale (category
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.Dv LC_NUMERIC ) .
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.Sh RETURN VALUES
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The
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.Fn strtod ,
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.Fn strtof ,
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and
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.Fn strtold
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functions return the converted value, if any.
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.Pp
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If
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.Fa endptr
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is not
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.Dv NULL ,
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a pointer to the character after the last character used
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in the conversion is stored in the location referenced by
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.Fa endptr .
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.Pp
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If no conversion is performed, zero is returned and the value of
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.Fa nptr
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is stored in the location referenced by
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.Fa endptr .
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.Pp
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If the correct value would cause overflow, plus or minus
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.Dv HUGE_VAL ,
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.Dv HUGE_VALF ,
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or
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.Dv HUGE_VALL
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is returned (according to the sign and type of the return value), and
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.Er ERANGE
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is stored in
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.Va errno .
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If the correct value would cause underflow, zero is
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returned and
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.Er ERANGE
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is stored in
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.Va errno .
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.Sh ERRORS
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.Bl -tag -width Er
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.It Bq Er ERANGE
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Overflow or underflow occurred.
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.El
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.Sh SEE ALSO
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.Xr atof 3 ,
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.Xr atoi 3 ,
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.Xr atol 3 ,
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.Xr nan 3 ,
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.Xr strtol 3 ,
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.Xr strtoul 3 ,
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.Xr wcstod 3
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.Sh STANDARDS
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The
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.Fn strtod
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function
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conforms to
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.St -isoC-99 .
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.Sh AUTHORS
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The author of this software is
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.An David M. Gay .
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.Bd -literal
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Copyright (c) 1998 by Lucent Technologies
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All Rights Reserved
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Permission to use, copy, modify, and distribute this software and
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its documentation for any purpose and without fee is hereby
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granted, provided that the above copyright notice appear in all
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copies and that both that the copyright notice and this
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permission notice and warranty disclaimer appear in supporting
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documentation, and that the name of Lucent or any of its entities
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not be used in advertising or publicity pertaining to
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distribution of the software without specific, written prior
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permission.
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LUCENT DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
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INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS.
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IN NO EVENT SHALL LUCENT OR ANY OF ITS ENTITIES BE LIABLE FOR ANY
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SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER
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IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
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ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF
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THIS SOFTWARE.
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.Ed
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