Creating a excutable shell script

When writing shell scripts you can use .sh file extension and run using the sh command.
Example:
sh helloWorld.sh

You can make your shell script executable and run using ./
Example:
./helloWorld.sh

To make it like this we need to do 2 things:
Change the file permissions
Define the interpreter/shell we will be using in the script.

Changing the file permissions:
Run the command:
chmod 0755 helloWorld.sh
This will allow all users to run the script

To only allow the current user to run the script run:
chmod 0700 helloWorld.sh

Defining the shell within the script:
Add the following line to the start of the script
#!/bin/sh
Or
#!/bin/bash
Depending on which one you are using.

Now you can run your script by typing
./helloWorld.sh