Access and addition of two elements of integer array in bash

Question

I could not access elements from the integer array in bash and add the two.

This is my code:

popA[$n]=${popA[$n]} - ${popA[($n)-1]};

chepner · Accepted Answer · 2015-08-15 19:48:44Z

4

You are accessing the elements correctly, but you need an arithmetic expression to actually perform math:

popA[$n]=$(( ${popA[$n]} - ${popA[$n - 1]} ))

In case you are wondering why you don't need $((...)) for the n-1 index, the array subscript is automatically evaluated as an arithmetic expression for an indexed array. (The parentheses around $n are unnecessary, although harmless.)

answered Aug 15, 2015 at 19:48

chepner

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