Shell tip: Clear the command history and screen when you log out

Posted on in Categories File system, FreeBSD, Gentoo Linux, RedHat/Fedora Linux, Security, Shell scripting, Sys admin, Tips, Tuning, UNIX last updated May 15, 2007

For security reason you may want to clear the history file and the screen when you hit CTRL+D or type logout command as you don’t want to left content on screen (i..e avoid an information leak). Some Linux distro may clear the screen but others do not clear the screen when you logout.

When a login shell exits, bash reads and executes commands from the file ~/.bash_logout, if it exists. Basically you can use this file as the individual login shell cleanup file, executed when a login shell exits.

There is a simple solution to this problem, open your ~/.bash_logout file:
$ vi ~/.bash_logout
Append any one of the following command:
/usr/bin/clear_console
OR
/usr/bin/clear
You can also reset your history by appending following commands:
>~/.bash_history
>~/.mysql_history
sync;

First one will clear bash history and 2nd command will clear mysql command history using shell REDIRECTION operator >.

Posted by: Vivek Gite

The author is the creator of nixCraft and a seasoned sysadmin and a trainer for the Linux operating system/Unix shell scripting. He has worked with global clients and in various industries, including IT, education, defense and space research, and the nonprofit sector. Follow him on Twitter, Facebook, Google+.

17 comment

  1. The >~/.bash_history thing seems a slightly odd way of doing things, why not put “unset HISTFILE” in your .bashrc file, since .bash_logout will be run about the time .bash_history is written, so it may (though probably not) end up wiping the file before it’s written.
    Or what I prefer to do, rm .bash_history and then :
    ln -s /dev/null .bash_history

  2. > maybe history -c is an option…
    I like it.

    I’ve typically used:
    HISTFILE=/do/not/use/$RANDOM/$RANDOM

    > why not put “unset HISTFILE” in your .bashrc file, since .bash_logout
    > will be run about the time .bash_history is written [snip]

    Similar idea, but IIRC I’ve had problems with unsetting the HISTFILE — but that was probably ~15 years ago under Korn shell.

    I also tried a touch-then-delete approach in my profile, I think that one worked fine, but the $RANDOM is my default.

    Incidentally, I try to always do this for root, since on rare occasions passwords are on the command line.

  3. ever heard of kill -9 $$ ?

    It logs you out and clear the history.

    It seems to kill bash, echo $$ gives you the bash PID

    A friend of mine showed me this once, but I never completely get how it works, if someone can explain, please do so…

  4. Kumar asked about clearing the information from his putty window.

    To do so –
    1. Right click on the top bar of the putty window
    2. A Context menu will appear
    3. Select “Clear Scrollback”

    This will erase all details of your session from putty’s scrollback buffer.

  5. gnudiego you are correct, it does not work with gnome-terminal which is installed as a default for linux mint. I am considering removing the gnome-terminal but would like to know what the best alternative would be.

    Thanks.

  6. I placed “history -r” in .bash_logout

    I then added the following to .bashrc, just in case something did get written to .bash_history. It checks if you have any other sessions open, if you don’t it clears the .bash_history file.

    if [ w | grep -c $(whoami) = 1 ]; then
    >/home/$(whoami)/.bash_history
    fi

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