iterations_even_odd

  i=0; FILES=$(ls -tr ./); for FILE in $FILES; do i=$(($i + 1)); if [$(($i % 2)) = 0]; then echo"$i$FILE"; fi; done;

  outputs:
  ==>
  -bash: [0: command not found
  -bash: [1: command not found
  -bash: [0: command not found
  ...
  ...
  ...
  <==

renamer.sh

#!/bin/bash

i=0
FILES=$(ls -tr ./)
for FILE in $FILES; do
  i=$(($i + 1))
  isEven=$(($i % 2))
  if [ "$isEven" -eq 0 ]; then
    echo "$i$FILE"
  fi
done