Bash 脚本从 AWS 命令行客户端循环访问 output

Question

I'm getting a list of EC2 instances and then trying to loop through them but for some reason I'm not able to get the loop to work.

output="$(aws ec2 describe-instances --filters 'Name=tag:Environment,Values=development' --query '[Reservations[*].Instances[*].PublicDnsName]' --output text)"

echo $output displays something like:

ec2-55-55-555-555.eu-west-1.compute.amazonaws.com
ec2-66-66-666-666.eu-west-1.compute.amazonaws.com

Then I create an array like this:

instances=(${output//'\n'/ })

echo ${instances[0]} and echo ${instances[1]} gives the correct output.

And then try to iterate through the array:

for i in $instances; do echo instance: "$i"; done

But I get:

instance: ec2-55-55-555-555.eu-west-1.compute.amazonaws.com ec2-66-66-666-666.eu-west-1.compute.amazonaws.com

Instead of:

instance: ec2-55-55-555-555.eu-west-1.compute.amazonaws.com
instance: ec2-66-66-666-666.eu-west-1.compute.amazonaws.com

What am I doing wrong? And is there a better way to loop through the results, maybe rather using the json output format?

Answer 1

I am not sure if you got an answer for this question. Will this help?

for dns in $(aws ec2 describe-instances --region ap-northeast-1 --query 'Reservations[*].Instances[*].PublicDnsName' --output text) ; do echo $dns ; done

Answer 2

For windows cli:

aws ec2 describe-instances --query "Reservations[].Instances[].InstanceId" > instances

FOR /f %i IN (instances) DO aws ec2 terminate-instances --instance-ids %i

Answer 3

This also works for me, add it to a bash array:

for instance in $(aws ec2 describe-instances --filters "Name=tag:Application,Values=yourValue" "Name=tag:Environment,Values=development" --query 'Reservations[*].Instances[*].InstanceId' --output text); do envInstances+=(${instance}); done

for i in ${envInstances[@]}; do echo "hello $i"; done

hello i-instance1
hello i-instance12
hello i-instance16

Answer 4

Not sure if you just gave up, but in BASH, better to just do this:

OUTPUT=($(aws ec2 describe-instances --filters 'Name=tag:Environment,Values=development' --query '[Reservations[ ].Instances[ ].PublicDnsName]' --output text))

then (if you want a count)

echo "${#OUTPUT[@]} instances found."

Good luck!