1

Can the below code be easily achieved with minimum coding.

$ cluster1=(x y)
$ cluster2=(a b)
$ cluster3=(m)

$ my=$((${cluster1[0]+1}+${cluster2[0]+1}+${cluster2[0]+1}))

$ echo $my
3

$ my=$((${cluster1[1]+1}+${cluster2[1]+1}+${cluster3[1]+1}))
-bash: 1+1+: syntax error: operand expected (error token is "+")
  • You can't use the second element of an array of one. – Gerard H. Pille Sep 15 '18 at 6:03
  • Yes, I was hoping if it can somehow return 0 or some other value , if element doesn't exist – Bharat Sep 15 '18 at 6:10
  • What exactly do you want to do? – Mark Smith Sep 15 '18 at 6:31
  • I wanted to count how many arrays has elements at first index, same way on second index with one liner code. – Bharat Sep 15 '18 at 6:39
0

Your code is generating a syntax error for each element that is not set.

$ echo "${cluster1[0]+1}+${cluster2[0]+1}+${cluster2[0]+1}"
1+1+1

$ echo "${cluster1[1]+1}+${cluster2[1]+1}+${cluster3[1]+1}"
1+1+

It would be better to count the set elements instead of trying to calculate with a generated expression in this case:

#!/bin/bash

cluster1=(x y)
cluster2=(a b)
cluster3=(m)

for (( i = 0; i < 3; ++i )); do
    is_set=( ${cluster1[i]+"1"} ${cluster2[i]+"1"} ${cluster3[i]+"1"} )
    printf 'i=%d:\t%d\n' "$i" "${#is_set[@]}"
done

This creates a new array, is_set, that will contain a 1 for each array that contains an element at index i. The 1 is unimportant and could be any string. The number of elements in the is_set array (${#is_set[@]}) is then the number of set elements from the cluster arrays at that index.

Testing:

$ bash script.sh
i=0:    3
i=1:    2
i=2:    0
  • nice... my=(${cluster1[1]+1} ${cluster2[1]+1} ${cluster3[1]+1}) ; echo ${#my[@]} – Bharat Sep 15 '18 at 8:42
1

May be a dirty trick, but how about prefixing a 0 (safe as the "Alternate Value" is a valid octal number):

my=$((0${cluster1[1]+1}+0${cluster2[1]+1}+0${cluster3[1]+1}))
echo $my
2
  • it's also nice.. – Bharat Sep 15 '18 at 8:45

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