How to call a shell script from another shell script

Note: Make sure to add #!/bin/bash to the first line of the script and make it executable through chmod 700 <path to script>.

1. <path to script> or /bin/bash <path to script> or <scriptname> (add script to $PATH environment variable and call as normal command)
   - child script is executed in a new shell, changes in child script does not affect parent script
   - can be executed asynchronously through background command
2. <path to script> &
   - same as no. 1 but executes child script on background
3. source <path to script> or . <path to script>
   - child script is executed in a current shell
   - context is same as parent script (vars and functions of child script becomes visible on parent script)
   - exit call in child script will also exit the parent script
4. exec <path to script>
   - terminates the current shell and executes on a new shell