Unix in a Nutshell, 4th Edition

Name

case

Synopsis

    case value in
     pattern1) cmds1;;
     pattern2) cmds2;;
     .
     .
     .
    esac

Execute the first set of commands (cmds1) if value matches pattern1, execute the second set of commands (cmds2) if value matches pattern2, etc. Be sure the last command in each set ends with ;;. value is typically a positional parameter or other shell variable. cmds are typically Unix commands, shell programming commands, or variable assignments. Patterns can use file-generation metacharacters. Multiple patterns (separated by |) can be specified on the same line; in this case, the associated cmds are executed whenever value matches any of these patterns. See the Examples here and under eval.

The shells allow pattern to be preceded by an optional open parenthesis, as in ( pattern ). In Bash and ksh88, it’s necessary for balancing parentheses inside a $() construct.

The Korn shell allows a case to end with ;& instead of ;;. In such cases control “falls through” to the group of statements for the next pattern.

Examples

Check first command-line argument and take appropriate action:

    case $1 in     # Match the first arg
        no|yes) response=1;;
        -[tT])  table=TRUE;;
        *)      echo "unknown option"; exit 1;;
    esac

Read user-supplied lines until user exits:

    while :        # Null command; always true
    do
       printf "Type . to finish ==> "
       read line
       case "$line" in
          .) echo "Message done"
             break ;;
          *) echo "$line" >> $message ;;
       esac
    done