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A very convenient feature
of BASH is history.

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Any command that you type is stored in history,
and this history is updated to the bash history file

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once you close your session. So anytime you exit,
the history file is updated. And the next time you

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open a new session, you still have access to
the commands that were used in the previous session.

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The history command is what you can
use to repeat commands from this file.

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Use history C to
clear the current history.

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Use history W to write the current history,
which shouldn't be necessary because it's normally done automatically.

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And use history D to
delete a specific line from history.

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Also, you can use control r for
the reverse isearch exclamation mark for followed

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by a number to repeat a specific
line from history. Let me show you.

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So let me start by
using till on Tilde BASH history.

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And what do we see? Well, we see
the last couple of lines in my history

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and oh, that is vim demo file
and vim trial. That's a long time ago.

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And you know why? Well, that is
because I haven't closed my session since.

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If I type history, I can see all the
commands that I have typed so far if I

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want to save them. I use history W
to commit my current history to the history file.

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Now, I like Control R.
Control R is the reverse isearch.

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In this reverse isearch, if I'm looking for the
last awk command, for instance, I just type awk and

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there we can see that it is searching backward
for the last command where it has found awg.

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Now, this reverse isearch is
searching for a text pattern anywhere

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in the command, not necessarily
at the start of the command.

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If you want to repeat it,
you can use Control R and Ctrl

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R and Ctrl R again until
you found the command that you wanted.

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What do we have here? That's a command that is
not complete. So let me Control C that another convenient thing

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that you can do in history is exclamation followed by
a number. I'm using exclamation 416 to repeat command 417 again.

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Look at that, my
home directory has changed.

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I didn't want that. So let's
get back to my home directory.

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There is one more thing that is convenient
in history and that you need to know about.

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And that is the way
to remove commands from history.

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I'm going to do that
on the relatively innocent command 417.

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So I'm using history D417 and you might
be wondering, when do I ever need to

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remove something from history? Well, that's very convenient
if you did something really silly or if

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you have entered a clear text password and
you want to make sure that it is

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not going to be saved. And that's
how you work with history. Very convenient feature.

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I'm sure you are going
to like it a lot.