Loop Through Array Values and Assign At The Same Time in Bash

bluethundr · 08-28-2018, 09:39 AM

Hello,

I am allowing users of our AWS accounts to attach multiple security groups to an AWS instance with a bash script I'm writing.

These lines get the user to specify how many SG's they want to use:

Code:

printf "Enter number of security groups to add: "
  read -r sg_answer


while [ "$sg_startvalue" -le "$sg_answer" ]; do
      read -rp "Enter Security Group ID $sg_startvalue : " security_group && security_groups+=("$security_group")
      sg_startvalue=$((sg_startvalue+1))
    done

And these lines add the security groups to the instance:

Code:

for aws_sg in "${security_groups[@]}"; do
         printf "Adding %s to %s\\n" "$tag_instance_id" "$aws_sg"
         aws ec2 modify-instance-attribute --instance-id "$tag_instance_id" --groups "$aws_sg" --profile="$aws_key"
         sleep 5
      done

Problem is this AWS command (aws ec2 mofify-instance-attribute) needs to add ALL of the security groups at the same time. I won't know how many security groups the user is adding ahead of time.

If you run that command in a loop (as I'm doing here) each time that command runs it replaces the $aws_sg value that preceded it.

How do I gather the arbitrary number of aws_sg values into one line that I can use with aws ec2 modify-instance-attribute?

ondoho · 08-28-2018, 12:58 PM

i'm not sure i understand, but to literally answer "Loop Through Array Values and Assign At The Same Time in Bash":

Code:

for ((i=0;i<${#array[@]};i++)); do
    array[i]="somevalue"
done