bash "for loop"

Question

When I do,

for ((i=0; i<"${ARRAY}"; i+=2))
do
    echo $i
    echo ${ARRAY[$i]}
done

echo $i works as I expected, also echo ${ARRAY[0]} works, but with $i as iterator i see only blank lines. How to write the for loop correctly?

Answer 1

Try the below script. It should work.

declare -a array=('1' '2' '3' '4' '5' '6' '7' '8' '9' '10' '11')
for ((i=0; i<=${#array[@]}; i+=2 )) ;
  do
     echo "Current Iterator i value:" $i
     echo "Array element at this position:" ${array[$i]}
 done

Output of the script

Current Iterator i value: 0
Array element at this position: 1
Current Iterator i value: 2
Array element at this position: 3
Current Iterator i value: 4
Array element at this position: 5
Current Iterator i value: 6
Array element at this position: 7
Current Iterator i value: 8
Array element at this position: 9
Current Iterator i value: 10
Array element at this position: 11

Explanation

I have initially declared an array with 11 elements.

From your question, I believe you are trying to iterate through all the elements available in the array.

${#array[@]} - This is used to determine the length of the array.

${array[$i]} - This is used to print an element at a particular index.