417 lines
11 KiB
Groff
417 lines
11 KiB
Groff
.\" $FreeBSD$
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.\" $OpenBSD: bc.1,v 1.32 2015/11/17 05:45:35 mmcc Exp $
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.\"
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.\" Copyright (C) Caldera International Inc. 2001-2002.
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.\" All rights reserved.
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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 and documentation must retain the above
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.\" copyright 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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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed or owned by Caldera
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.\" International, Inc.
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.\" 4. Neither the name of Caldera International, Inc. nor the names of other
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.\" contributors may be used to endorse or promote products derived from
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.\" this software without specific prior written permission.
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.\"
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.\" USE OF THE SOFTWARE PROVIDED FOR UNDER THIS LICENSE BY CALDERA
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.\" INTERNATIONAL, INC. AND CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR
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.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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.\" IN NO EVENT SHALL CALDERA INTERNATIONAL, INC. BE LIABLE FOR ANY DIRECT,
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.\" INDIRECT INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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.\" (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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.\" 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,
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.\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
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.\" IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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.\" POSSIBILITY OF SUCH DAMAGE.
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.\"
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.\" @(#)bc.1 6.8 (Berkeley) 8/8/91
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.\"
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.Dd November 21, 2015
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.Dt BC 1
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.Os
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.Sh NAME
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.Nm bc
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.Nd arbitrary-precision arithmetic language and calculator
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.Sh SYNOPSIS
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.Nm bc
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.Op Fl chlv
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.Op Fl e Ar expression
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.Op Ar file ...
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.Sh DESCRIPTION
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.Nm
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is an interactive processor for a language which resembles
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C but provides unlimited precision arithmetic.
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It takes input from any expressions on the command line and
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any files given, then reads the standard input.
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.Pp
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Options available:
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.Bl -tag -width Ds
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.It Fl c
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.Nm
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is actually a preprocessor for
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.Xr dc 1 ,
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which it invokes automatically, unless the
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.Fl c
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.Pq compile only
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option is present.
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In this case the generated
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.Xr dc 1
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instructions are sent to the standard output,
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instead of being interpreted by a running
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.Xr dc 1
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process.
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.It Fl e Ar expression , Fl Fl expression Ar expression
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Evaluate
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.Ar expression .
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If multiple
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.Fl e
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options are specified, they are processed in the order given,
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separated by newlines.
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.It Fl h , Fl Fl help
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Prints usage information.
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.It Fl l , Fl Fl mathlib
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Allow specification of an arbitrary precision math library.
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The definitions in the library are available to command line
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expressions.
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.It Fl v , Fl Fl version
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Prints version information.
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.El
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.Pp
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The syntax for
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.Nm
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programs is as follows:
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.Sq L
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means letter a-z;
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.Sq E
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means expression;
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.Sq S
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means statement.
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As a non-portable extension, it is possible to use long names
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in addition to single letter names.
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A long name is a sequence starting with a lowercase letter
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followed by any number of lowercase letters and digits.
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The underscore character
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.Pq Sq _
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counts as a letter.
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.Pp
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Comments
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.Bd -unfilled -offset indent -compact
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are enclosed in /* and */
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are enclosed in # and the next newline
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.Ed
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.Pp
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The newline is not part of the line comment,
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which in itself is a non-portable extension.
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.Pp
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Names
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.Bd -unfilled -offset indent -compact
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simple variables: L
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array elements: L [ E ]
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The words `ibase', `obase', and `scale'
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The word `last' or a single dot
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.Ed
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.Pp
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Other operands
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.Bd -unfilled -offset indent -compact
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arbitrarily long numbers with optional sign and decimal point
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( E )
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sqrt ( E )
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length ( E ) number of significant decimal digits
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scale ( E ) number of digits right of decimal point
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L ( E , ... , E )
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.Ed
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.Pp
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The sequence
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.Sq \e<newline><whitespace>
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is ignored within numbers.
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.Pp
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Operators
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.Pp
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The following arithmetic and logical operators can be used.
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The semantics of the operators is the same as in the C language.
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They are listed in order of decreasing precedence.
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Operators in the same group have the same precedence.
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.Bl -column "= += \-= *= /= %= ^=" "Associativity" "multiply, divide, modulus" -offset indent
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.It Sy "Operator" Ta Sy "Associativity" Ta Sy "Description"
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.It "++ \-\-" Ta "none" Ta "increment, decrement"
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.It "\-" Ta "none" Ta "unary minus"
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.It "^" Ta "right" Ta "power"
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.It "* / %" Ta "left" Ta "multiply, divide, modulus"
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.It "+ \-" Ta "left" Ta "plus, minus"
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.It "= += -= *= /= %= ^=" Ta "right" Ta "assignment"
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.It "== <= >= != < >" Ta "none" Ta "relational"
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.It "!" Ta "none" Ta "boolean not"
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.It "&&" Ta "left" Ta "boolean and"
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.It "||" Ta "left" Ta "boolean or"
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.El
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.Pp
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Note the following:
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.Bl -bullet -offset indent
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.It
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The relational operators may appear in any expression.
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The
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.St -p1003.1-2008
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standard only allows them in the conditional expression of an
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.Sq if ,
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.Sq while
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or
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.Sq for
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statement.
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.It
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The relational operators have a lower precedence than the assignment
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operators.
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This has the consequence that the expression
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.Sy a = b < c
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is interpreted as
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.Sy (a = b) < c ,
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which is probably not what the programmer intended.
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.It
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In contrast with the C language, the relational operators all have
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the same precedence, and are non-associative.
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The expression
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.Sy a < b < c
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will produce a syntax error.
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.It
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The boolean operators (!, && and ||) are non-portable extensions.
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.It
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The boolean not
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(!) operator has much lower precedence than the same operator in the
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C language.
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This has the consequence that the expression
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.Sy !a < b
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is interpreted as
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.Sy !(a < b) .
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Prudent programmers use parentheses when writing expressions involving
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boolean operators.
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.El
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.Pp
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Statements
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.Bd -unfilled -offset indent -compact
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E
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{ S ; ... ; S }
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if ( E ) S
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if ( E ) S else S
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while ( E ) S
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for ( E ; E ; E ) S
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null statement
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break
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continue
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quit
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a string of characters, enclosed in double quotes
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print E ,..., E
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.Ed
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.Pp
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A string may contain any character, except double quote.
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The if statement with an else branch is a non-portable extension.
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All three E's in a for statement may be empty.
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This is a non-portable extension.
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The continue and print statements are also non-portable extensions.
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.Pp
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The print statement takes a list of comma-separated expressions.
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Each expression in the list is evaluated and the computed
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value is printed and assigned to the variable `last'.
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No trailing newline is printed.
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The expression may also be a string enclosed in double quotes.
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Within these strings the following escape sequences may be used:
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.Sq \ea
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for bell (alert),
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.Sq \eb
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for backspace,
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.Sq \ef
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for formfeed,
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.Sq \en
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for newline,
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.Sq \er
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for carriage return,
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.Sq \et
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for tab,
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.Sq \eq
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for double quote and
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.Sq \e\e
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for backslash.
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Any other character following a backslash will be ignored.
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Strings will not be assigned to `last'.
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.Pp
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Function definitions
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.Bd -unfilled -offset indent
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define L ( L ,..., L ) {
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auto L, ... , L
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S; ... S
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return ( E )
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}
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.Ed
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.Pp
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As a non-portable extension, the opening brace of the define statement
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may appear on the next line.
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The return statement may also appear in the following forms:
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.Bd -unfilled -offset indent
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return
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return ()
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return E
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.Ed
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.Pp
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The first two are equivalent to the statement
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.Dq return 0 .
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The last form is a non-portable extension.
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Not specifying a return statement is equivalent to writing
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.Dq return (0) .
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.Pp
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Functions available in the math library, which is loaded by specifying the
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.Fl l
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flag on the command line
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.Pp
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.Bl -tag -width j(n,x) -offset indent -compact
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.It s(x)
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sine
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.It c(x)
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cosine
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.It e(x)
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exponential
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.It l(x)
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log
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.It a(x)
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arctangent
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.It j(n,x)
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Bessel function
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.El
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.Pp
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All function arguments are passed by value.
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.Pp
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The value of a statement that is an expression is printed
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unless the main operator is an assignment.
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The value printed is assigned to the special variable `last'.
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This is a non-portable extension.
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A single dot may be used as a synonym for `last'.
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Either semicolons or newlines may separate statements.
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Assignment to
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.Ar scale
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influences the number of digits to be retained on arithmetic
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operations in the manner of
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.Xr dc 1 .
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Assignments to
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.Ar ibase
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or
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.Ar obase
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set the input and output number radix respectively.
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.Pp
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The same letter may be used as an array, a function,
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and a simple variable simultaneously.
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All variables are global to the program.
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`Auto' variables are pushed down during function calls.
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When using arrays as function arguments
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or defining them as automatic variables,
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empty square brackets must follow the array name.
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.Pp
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For example
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.Bd -literal -offset indent
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scale = 20
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define e(x){
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auto a, b, c, i, s
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a = 1
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b = 1
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s = 1
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for(i=1; 1==1; i++){
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a = a*x
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b = b*i
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c = a/b
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if(c == 0) return(s)
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s = s+c
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}
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}
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.Ed
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.Pp
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defines a function to compute an approximate value of
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the exponential function and
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.Pp
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.Dl for(i=1; i<=10; i++) e(i)
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.Pp
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prints approximate values of the exponential function of
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the first ten integers.
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.Bd -literal -offset indent
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$ bc -l -e 'scale = 500; 2 * a(2^10000)' -e quit
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.Ed
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.Pp
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prints an approximation of pi.
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.Sh COMMAND LINE EDITING
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.Nm
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supports interactive command line editing, via the
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.Xr editline 3
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library.
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It is enabled by default if input is from a tty.
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Previous lines can be recalled and edited with the arrow keys,
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and other GNU Emacs-style editing keys may be used as well.
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.Pp
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The
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.Xr editline 3
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library is configured with a
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.Pa .editrc
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file \- refer to
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.Xr editrc 5
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for more information.
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.Sh FILES
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.Bl -tag -width /usr/share/misc/bc.library -compact
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.It Pa /usr/share/misc/bc.library
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math library, read when the
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.Fl l
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option is specified on the command line.
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.El
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.Sh COMPATIBILITY
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The
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.Fl q
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and
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.Fl Fl quiet
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options are no-ops for compatibility with some other implementations of
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.Nm
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and their use is discouraged.
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.Sh SEE ALSO
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.Xr dc 1
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.Sh STANDARDS
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The
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.Nm
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utility is compliant with the
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.St -p1003.1-2008
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specification.
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.Pp
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The flags
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.Op Fl ce ,
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as well as the parts noted above,
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are extensions to that specification.
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.Sh HISTORY
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The
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.Nm
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command first appeared in
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.At v6 .
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A complete rewrite of the
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.Nm
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command first appeared in
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.Ox 3.5 .
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.Sh AUTHORS
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.An -nosplit
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The original version of the
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.Nm
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command was written by
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.An Robert Morris
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and
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.An Lorinda Cherry .
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The current version of the
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.Nm
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utility was written by
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.An Otto Moerbeek .
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.Sh BUGS
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The
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.Ql quit
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statement is interpreted when read, not when executed.
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.Pp
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Some non-portable extensions, as found in the GNU version of the
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.Nm
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utility are not implemented (yet).
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