case in Mac OS X

By: Strauss K in macos Tutorials on 2011-02-03

case is a keyword in shell scripting, including in Mac OS X, that is used for conditional branching. It is similar to a switch statement in other programming languages.

The basic syntax of case statement in Mac OS X is as follows:

case expression in
  pattern1)
    commands1
    ;;
  pattern2)
    commands2
    ;;
  ...
  *)
    default commands
    ;;
esac

Here, expression is the value that is being compared against different patterns. pattern1, pattern2, and so on are the different patterns that are being matched against the expression. commands1, commands2, and so on are the commands that are executed if a pattern matches. The ;; after each set of commands separates each pattern and its commands.

The * in the final pattern is a wildcard pattern that matches anything that didn't match any of the other patterns. The commands after it are the default commands that are executed if no other patterns match.

Here's an example:

#!/bin/bash

echo "Enter a number between 1 and 3: "
read num

case $num in
  1)
    echo "You entered 1."
    ;;
  2)
    echo "You entered 2."
    ;;
  3)
    echo "You entered 3."
    ;;
  *)
    echo "You did not enter a number between 1 and 3."
    ;;
esac

In this example, the user enters a number between 1 and 3, and the script uses a case statement to match it against the different patterns. If the user entered 1, it would print "You entered 1.", and so on. If the user entered anything else, it would print "You did not enter a number between 1 and 3."

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