Table 10-2. Special editing variables

      # Quoted from Page 98 of
      # The New KornShell Command and Programming Language

 1    typeset -A Keytable
 2    trap 'eval "${Keytable[${.sh.edchar}]}"' KEYBD
 3    function keybind # key [action]
 4    {
 5         typeset key=$(print -f "%q" "$2")
 6         case $# in
 7         2)      Keytable[$1]=' .sh.edchar=${.sh.edmode}'"$key"
 8                 ;;
 9         1)      unset Keytable[$1]
10                 ;;
11         *)      print -u2 "Usage: $0 key [action]"
12                 return 2 # usage errors return 2 by default
13                 ;;
14         esac
15    }

This is an interesting function. Let's go through it line by line. Line 1 creates an associative array to act as a table of key/action pairs. Line 2 sets the KEYBD trap. It gets the action out of the associative array and then executes it using eval. Line 3 starts the keybind function, which takes one or two arguments. With two arguments, the second argument is first quoted appropriately (line 5 -- the key variable would have been better-named action). Line 7 then creates the entry in the array, using $1 (the user key sequence) as the index, and quoted action as the value to assign to .sh.edchar. Note how ${.sh.mode} is also included. This has the effect of forcing a switch to command mode for the vi editing mode. It is this generated assignment statement that is evaled every time the trap executes.

The rest of the function is mostly bookkeeping: with one argument (line 9), the given entry in the Keytable array is removed. If more than two arguments (line 11), keybind prints a message and then returns the (false) value 2.