Propagate value of variable to outside of the loop [duplicate]

Answer 1

Alternatively, you can move the echo statements inside the subshell:

dpkg --list |grep linux-image |grep "ii  " | (
  let i=0
  declare -a arr

  while read line
  do
    arr=(${line})
    let i=i+1
    _constr+="${arr[2]} "
  done
  echo $i
  echo ${_constr}
)

Note the insertion of the parenthesis to explicitly define where the subshell begins and ends.