Before you start shell scripting.....

• Permissions

          read - 4                            
         write - 2
         execute -1

         ex:   Give all the permission to Owner, give only read and execute permission to Group and       others, total becomes 755

                  chmod 755 file.sh

• Comment         #this is how u comment in shell

• Shell scripting

         #!/bin/bash                  //always mention in the first line of bash file.
       
          chmod 755 file.sh        //give permission to bash file
       
         ./file.sh                        //run bash file