October 2009
Beginner to intermediate
242 pages
5h 4m
English
Content preview from Pro Bash Programming: Scripting the GNU/Linux Shell
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
Start your free trial
CHAPTER 3Looping and Branching
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 loop (while, until, and for) and three types of conditional execution (if, case, and the conditional operators && and ||, which mean AND and OR, respectively). With the exception of for and case, the exit status of a command controls the behavior.
Exit Status
You can test the success of a command directly using the shell keywords while, until, and if or with the control operators && and ||. The ...