AWS CLI で現在停止中で30日以上前に起動されたインスタンスを取得するワンライナー ref: http://qiita.com/simeji/items/3d680c3a59897700f43c

file0.txt

$ ago=30;date -v-${ago}d > /dev/null 2>&1 && DATE=`date -v-${ago}d +%Y-%m-%d` || DATE=`date --date="-${ago} days" +%Y-%m-%d`; aws ec2 describe-instances --filter Name=instance-state-name,Values=stopped --query "Reservations[].Instances[?LaunchTime<='$DATE'][].{InstanceId: InstanceId,PrivateIpAddress: PrivateIpAddress,LaunchTime: LaunchTime}"

file1.txt

[
    {
        "InstanceId": "i-4xxxxxb5",
        "LaunchTime": "2015-08-02T16:31:32.000Z",
        "PrivateIpAddress": "172.31.0.200"
    },
    {
        "InstanceId": "i-dxxxxx2e",
        "LaunchTime": "2015-06-20T09:32:45.000Z",
        "PrivateIpAddress": "172.31.0.79"
    }
]

file2.txt

$ echo $DATE
>> 2015-08-18

file3.txt

[
    {
        "InstanceId": "i-dxxxxx2e",
        "LaunchTime": "2015-06-20T09:32:45.000Z",
        "PrivateIpAddress": "172.30.0.79"
    }
]

file4.txt

$ echo $DATE
2015-07-19