shell script compare two array of number

Question

i have two array of numbers, first array have all numbers while the second has a subset of first one, how can i write a script to find the missing number which exist in the first array but not in the second array?

Array 1: [0, 1, 2, ..79] Array 2: [1, 12, 33, 54,60, 71]

i googled around and tried different approaches i found but none of them worked

1.

declare -a array3
for i in "${array1[@]}"
  if [[ "${array2[@]}" =~ "$i" || "${array2[${#array2[@]}-1]}" == "$i" ]]; then
  else
      array3+=("$i") 
  fi
done

2.

array3=()
for i in "${array1[@]}";do
  skip=
  for j in "$array2[@]";do
     [[ $i == $j ]] && { skip=1; break; }
  done
  [[ -n $skip ]] || array3+=("$i")
done
declare -p array3

i m new to bash script, please help!

Are the elements in each array sorted? If so, you'll need to run a loop with, say, index $i for array1 and $j for array2, and you will either find that $array1[$i] is smaller than $array2[$j, or equal to it, or larger than it. If the number in $array1[$i] is smaller, print it and increment $i; if the values are equal, increment both $i and $j; if it is larger, increment $j. Stop when you reach the end of either array. — Jonathan Leffler
– Jonathan Leffler, Commented Mar 6, 2015 at 16:58

anubhava · Accepted Answer · 2015-03-06 17:07:31Z

4

One way to get array differential is using comm:

array1=(0 1 2 3 4 5 6 7 8 9 10 11 12)
array2=(0 1 3 4 6 7 10 12)

comm -23 <(printf "%s\n" "${array1[@]}" | sort) <(printf "%s\n" "${array2[@]}" | sort) | sort -n

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answered Mar 6, 2015 at 17:07

anubhava

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