SED

 1) how to ignore sed operation in last line alone

# sed -e "$ ! s/a/b/"

2) SED Remove last character from line 

# sed 's/.$//'

 {

    "Version": "2024-02-17",

    "Statement": [

        {

            "Sid": "AllowLogCreation",

            "Effect": "Allow",

            "Action": [

                "logs:PutLogEvents",

                "logs:CreateLogStream",

                "logs:CreateLogGroup"

            ],

            "Resource": [

                "arn:aws:logs:*:*:*"

            ]

        },

        {

            "Sid": "AllowStartEc2",

            "Effect": "Allow",

            "Action": [

                "ec2:Stop*",

                "ec2:DescribeInstances"

            ],

            "Resource": [

                "*"

            ]

        }

    ]

  }

https://stackoverflow.com/questions/40040985/how-to-find-instances-that-dont-have-a-tag-using-boto3

 import boto3

client=boto3.client('ec2')

def lambda_handler(event, context):

    instances = [i for i in boto3.resource('ec2', region_name='ap-south-1').instances.all()]

    # Print instance_id of instances that do not have a Tag of Key='Foo'

    for i in instances:

        if i.tags is not None and 'resource' not in [t['Key'] for t in i.tags]:

            print (i.instance_id)

            ids=[]

            ids.append(i.instance_id)

            print (ids)

            client.stop_instances(InstanceIds=ids)

       #     client.stop_instances(i.instance_id)

 

    #ec2= boto3.resource('ec2', region_name = 'ap-south-1')

    #for each in ec2.instances.all():

     #   print (each.id)

Lookbehind syntax to ignore quotes

Lookbehind syntax to ignore quotes

-t -w -g london -s 'yesterday' -e 'yesterday' -f 100000"

-t -w -g london -s "yesterday" -e 'yesterday' -f 100000"

-t -w -g london -s yesterday -e yesterday -f 100000"

Task is to extract the word after "-s" 

Command : grep -oP "(?<=-s \"|-s '|-s )[^'\" ]*"

Explanation

(?<=          : is the syntax for lookbehind

s \"|-s '|-s  : or condition to search the word after -s
[^'\" ]        : 
Output
yesterday
yesterday
yesterday

Command 2 : grep -oP -- '-s\s*\K([^ ]+)' file | tr -d \'\"