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Bash input executes functions

How to execute functions in Bash based on argument.

There are 2 functions: build and terminate.

#!/bin/bash
build () {
 echo 'Building services'
}
terminate () {
 echo 'Terminating services'
}
if [ $1 == 'build' ]; then build
elif [ $1 == 'terminate' ]; then terminate
else echo 'Valid options are "build" or "terminate"'
fi

Execute a function based on argument.

$ bash test.sh build
Building services
 
$ bash test.sh terminate
Terminating services
 
$ bash test.sh anyother
Valid options are "build" or "terminate"

CloudFormation Userdata

Here’s another way to add startup scripts to your instance during creation.

      UserData:
        Fn::Base64: !Sub |
          #cloud-config
          repo_upgrade: none
 
          runcmd:
            # Cloud init startup script
            - "bash /root/setup.sh"
 
          write_files:
            # Cloud init startup script
            - owner: root:root
              permissions: '0644'
              path: /root/setup.sh
              content: |
                #! /bin/bash -x
          write_files:
            # Cloud init startup script
            - owner: root:root
              permissions: '0644'
              path: /root/setup.sh
              content: |
                #! /bin/bash -x
                # run your bash commands here
                date > log.txt
                uptime >>  log.txt

The above script creates a file setup.sh and executes it during instance creation. The output is dumped to log.txt file.