Summary Box
The C shell and bash can save copies of the
previous command lines you type. Later, you can ask for a copy of
some or all of a previous command line. That can save time and
retyping.
This feature is called history
substitution, and it's done
when you type a string that starts with an exclamation point
(!command). You can
think of it like variable substitution
($varname) (Section 35.9) or command substitution ('command') (Section 28.14): the shell replaces what you type (like
!$) with something else (in this case, part or all
of a previous command line).
Section 30.1 is an introduction to shell
history. These articles show lots of ways to use history
substitution:
-
We start with favorite uses from several contributors -- Section 30.3, Section 30.4, Section 30.5, and Section 30.6.
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Section 30.8 starts with a quick
introduction, then covers the full range of history substitutions
with a series of examples that show the different kinds of things you
can do with history.
(Back in Section 28.5 are examples of
csh/tcsh and
bash operators such as :r. Many
of these can be used to edit history substitutions.)
-
See an easy way to repeat a set of
csh/tcsh or
bash commands in Section 30.9.
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Each shell saves its own history. To pass a shell's
history to another shell, see Section 30.12
and Section 30.13.
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You don't have to use an exclamation point
(!) for history. Section 30.15 shows how to use some other character.
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The Korn shell does history in a different way. Section 30.14 introduces part of that: command-line editing
in ksh and bash.
One last note: putting the history number in
your prompt (Section 4.3) makes it easy
to reuse commands that haven't scrolled off your
screen.
-- JP
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