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77 lines
2.3 KiB
Plaintext
77 lines
2.3 KiB
Plaintext
*arith* *arithmetic* *arithmetic-expansion*
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#ARITHMETIC EXPANSION#
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Arithmetic expansion evaluates a mathematical expression and substitutes
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the result. The expression is subject to parameter expansion and command
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substitution before evaluation.
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`$((expression))`
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Example:
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`echo $((2 + 3))` # prints: 5
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`x=$((width * height))`
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==============================================================================
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1. Operators *arith-operators*
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The following operators are supported, listed from highest to lowest
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precedence:
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`( )` *arith-parens*
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Grouping. Override default precedence.
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Example:
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`echo $(( (2+3) * 4 ))` # prints: 20
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`*` `/` `%` *arith-muldivmod*
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Multiplication, division, and modulo (remainder).
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Example:
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`echo $((10 / 3))` # prints: 3
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`echo $((10 % 3))` # prints: 1
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`+` `-` *arith-addsub*
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Addition and subtraction.
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Example:
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`echo $((10 - 3 + 1))` # prints: 8
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==============================================================================
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2. Variables in Expressions *arith-variables*
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Variables can be referenced by name inside arithmetic expressions.
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They are expanded and converted to numbers.
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`x=10`
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`echo $(($x + 5))` # prints: 15
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`echo $((x + 5))` # also works
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If a variable is unset or not a valid number, an error is reported.
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==============================================================================
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3. Nesting *arith-nesting*
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Arithmetic expressions can be nested with parentheses to any depth:
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`echo $(( (1+2) * (3+4) ))` # prints: 21
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Arithmetic expansion can also appear inside other expansions:
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`echo "Total: $((price * qty))"`
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==============================================================================
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4. Whitespace *arith-whitespace*
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Whitespace inside `$((...))` is ignored and can be used freely for
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readability:
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`echo $((2+3))` # prints: 5
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`echo $(( 2 + 3 ))` # same result
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==============================================================================
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See also: |param| |redirect| |glob|
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