Conditionally perform a command, case will selectively execute the command-list corresponding to the first pattern that matches word.

      case word in [ [(] pattern [| pattern]...) command-list ;;]... esac

The `|’ is used to separate multiple patterns, and the `)’ operator terminates a pattern list. A list of patterns and an associated command-list is known as a clause. Each clause must be terminated with `;;’.

The word undergoes tilde expansion, parameter expansion, command substitution, arithmetic expansion, and quote removal before matching is attempted. Each pattern undergoes tilde expansion, parameter expansion, command substitution, and arithmetic expansion. There can be an arbitrary number of case clauses, each terminated by a `;;’. The first pattern that matches determines the command-list that is executed.

Here is an example using case in a script that could be used to describe one interesting feature of an animal:
echo -n “Enter the name of an animal: ”
echo -n “The $ANIMAL has ”
case $ANIMAL in
horse | dog | cat) echo -n “four”;;
man | kangaroo ) echo -n “two”;;
*) echo -n “an unknown number of”;;
echo ” legs.”
The return status is zero if no pattern is matched. Otherwise, the return status is the exit status of the command-list executed.