History Substitution
History substitution allows you to use words from previous command
lines in the command line you are currently typing. This makes it
easier to correct simple errors in complicated command lines. To do
this, the shell has a built-in mechanism that keeps track of some
number of the commands you have typed. For example, the command "set
history=10" in your '.cshrc' file will tell
the shell to remember the last 10 commands you have typed:
<![CDATA[
% history
1 ls
2 date
3 history
%
]]>
This shows that I have given 3 commands: "ls", "date", and "history".
A history substitution command begins with an exclamation point or
"bang sign" (!). The command "!!" will repeat your previous command.
If you give the "date" command and then "!!", the "date" program will
run again:
<![CDATA[
% date
Fri Sep 4 14:21:01 PDT 1992
% !!
date
Fri Sep 4 14:21:01 PDT 1992
%
]]>
Here are some ways you can use history substitutions:
- !!
- re-run the previous command
- !n
- re-run command on line number n (from the history listing)
- !string
- re-run last command beginning with string
- ^word1^word2
- In previous command, substitute word2 for word1.
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