#035 Case Statements

How to use case statements in the bash shell.

Notes

The case statement (aka switch statements) is better suited to handling complex conditionals than nexted if conditions. They also support regular-expression style pattern matching

Formally, the case statement is as follows (although normally written with line breaks between cases and commands):

case EXPRESSION in CASE1) COMMAND-LIST;; CASE2) COMMAND-LIST;; ... CASEN) COMMAND-LIST;; esac

Points to note:

• starts/ends with case/esac
• ;; is required between cases. Unlike other languages, it cannot be omitted to allow control flow from one case to another
• it branches to the first matching case. Later matches (if any) are ignored.
• *) case is often used as a catch-all default - equivalent of an else condition.

Example

See case_examples.sh for various pattern matching options.

$ ./case_examples.sh 123
123 is: under 7*
$ ./case_examples.sh 888
888 is: like 7* or 8*
$ ./case_examples.sh 9
9 is: like 9*
$ ./case_examples.sh a
a is: a or b
$ ./case_examples.sh abc
abc is: abc
$ ./case_examples.sh def
def is: def
$ ./case_examples.sh left-hand
left-hand is: like *hand
$ ./case_examples.sh
help is: (default)

The handle_emtpy_case.sh example demonstrates matching blank

$ ./handle_emtpy_case.sh abc
abc is: defined option: abc
$ ./handle_emtpy_case.sh ""
 is: blank option
$ ./handle_emtpy_case.sh xyz
xyz is: (default)

Credits and References

• Switch case with fallthrough?
• 7.3. Using case statements - Bash Guide for Beginners
• 5 Bash Case Statement Examples