At the heart of any programming language are iteration and conditional execution. Iteration is the repetition of a section of code until a condition changes. Conditional execution is making a choice between two or more actions (one of which may be to do nothing) based on a condition.
In the shell, there are three types of loops (while, until, and for) and three types of conditional execution (if, case, and the conditional operators && and ||, which mean AND and OR, respectively). Except for for and case, the exit status of a command ...
