Bash 5 reference · Shell Builtins and Syntax

$(( )) arithmetic (Bash syntax)

Evaluate integer arithmetic and comparisons with $(( )) and (( )); Bash has no floating point, so use awk or bc.

Bash 5

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Syntax

$(( EXPRESSION ))   (( EXPRESSION ))

Parameter	Description
`+ - * / % **`	Operators; / truncates.
`++ += -=`	Increment and compound assignment.
`(( a > b ))`	Comparison as a condition.

Integer maths

a=17 b=5
echo "$(( a / b )) rem $(( a % b )), power $(( 2 ** 10 ))"
(( a > b )) && echo 'a is bigger'

Output

3 rem 2, power 1024
a is bigger

Run this on your computer — see “Get Started” for setup.

Accumulate, with awk for decimals

total=0
for n in 4 8 15; do (( total += n )); done
echo "total $total, avg $(awk -v t=$total 'BEGIN { printf "%.2f", t / 3 }')"

Output

total 27, avg 9.00

Run this on your computer — see “Get Started” for setup.

${...} expansion · Defaults, length, substrings, prefix and suffix removal, search and replace, and case conversion on variables.
Bash Arithmetic · tutorial