Word designators are used to select desired words from the event.
A : separates the event specification from the word designator. It
may be omitted if the word designator begins with a ^, $,
*, -, or %. Words are numbered from the beginning
of the line, with the first word being denoted by 0 (zero). Words are
inserted into the current line separated by single spaces.
For example,
!!
!!:$
!$.
!fi:2
fi.
Here are the word designators:
0 (zero)
0th word. For many applications, this is the command word.
n
^
$
%
?string? search.
x-y
-y abbreviates 0-y.
*
0th. This is a synonym for 1-$.
It is not an error to use * if there is just one word in the event;
the empty string is returned in that case.
x*
x-$
x-
x-$ like x*, but omits the last word.
If a word designator is supplied without an event specification, the previous command is used as the event.