With the command reuse feature of the bash shell, it is easy to use a previous command again or to see what commands we have recently used.

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Check history's definition and usage

History File Location

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echo $HISTFILE
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the file that records the used commands

History Size

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2

echo $HISTSIZE
echo $HISTFILESIZE
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these two commands show the amount of the lines of commands they can keep

History List

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history
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shows all recently used commands

Run Previous Command

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!!    # Ctrl+P can achieve similar results
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!! reexecutes the ls command

Run Recorded Command

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!1    # runs the first recorded command
!-1    # runs the last recorded command
!N    # runs the command on N line

Delete Executed Command

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pwd    # this will be the previous command
ls; history -d $(history 1)    # $(history 1) retrieves the last command's line number
!!    # runs the previous command
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the previous command is pwd not ls

Run Commands Without Saving

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echo $HISTFILE
unset HISTFILE
echo $HISTFILE
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!! reexecutes the ls command

Empty History Records

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history -c    # takes effect after the user logged out
history -w    # saves the changes to the .bash_history file, so the action takes effect immediately

References 9.1 Bash History Facilities, 9.2 Bash History Builtins, 9.3.1 Event Designators

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