Arithmetic

• Arithmetic is normally done with the let command:

declare -i x=0

let "x = x + 1"

let x=$x+1

let x+=1

• You can enclose an arithmetic expression in (( ... )) as well, or in $[ ... ] or $(( ... )) to have the value returned.

• For example, these are the same. In each case, the x variable now holds the value that was displayed:

((x=x+1)); echo $x

echo $((x=x+1))

echo $[x=x+1]