A few things for you...

⟫ Wright your script with extension '.sh'

⟫ Start your script with #!/bin/bash (or #!/bin/'your shell_type)

⟫ Give your shell execute permission (sudo chmod 755)

⟫ There is three way to execue a shell script ...

                bash shell_script_name.sh
									
               ./shell_script_name.sh
									
	       path/of/your/shell/script/shell_script_name.sh