Eval

 

Definition: Evaluates an expression and returns the result.

 

OK, we’re not sure how often you need to evaluate an expression (such as a mathematical equation) and simply know whether that expression is true or false. If you doneed to do this, however, you can do so simply by using the – eqcomparison operator. For example, this command evaluates the expression  2 + 2 = 45and then stores the evaluation (true or false) in the variable $a:

 

 

When you run this command and then echo back the value of $ a youshould get the following: