To run a specific task or list of commands repetitively on bash script , you need to use on of this three constructions : for , while , until . Each one fits different situation as we will know now.
At times you need to specify different courses of action to be taken in a shell script, depending on the success or failure of a command. The if construction allows you to specify such conditions.
AWK is another popular stream editor, just similar to SED. The basic function of awk is to search files for lines or other text units containing one or more patterns. When a line matches one of the patterns, special actions are performed on that line.
Variable is a temporary store for a simple piece of information, making it easier to use and manage in scripts. Tow actions that we do with variables is setting a value for the variable, or reading its value .