How do I close a terminal without saving the history?

Question

More than once I've accidentally run a number of commands and polluted my bash history. How do I close my terminal without saving my bash history? I'm using Fedora.

Answer 1

There's more than a few ways to accomplish this.

Note: These options are not mutually exclusive; they can be used in any combination, or all at once.

Option 0

Delete the HISTFILE shell variable.

unset HISTFILE

According to the man page this will remove the shell's ability to automatically write any history to a file, regardless of if you set HISTFILE to something after unsetting it.

Option 1

If you're a perfectionist when it comes to cluttering up your history file, then what you can do is modify the HISTIGNORE variable to include globs of commands you don't want recorded. For instance, if you add HISTIGNORE='ls*:cd*' to your ~/.bashrc then any instance of ls and cd aren't inserted into your history file.

This variable respects extglob when turned on:

shopt -s extglob
# With `extglob` on I can use extended globs to ignore all:
# cd ..
# cd ../
# cd ..//
# cd ../..
# cd ../../
# cd ../..//
# etc.
HISTIGNORE='cd +(..|../)*(/)'

This will ignore cd .., cd ../, cd ../.., etc but leave cd myfolder.

More information on extended globs can be found in the bash man page.

Option 2

If you want to control on a command-by-command basis what commands get left out of your history, you can set HISTCONTROL='ignorespace' which will omit any command lines starting with a space. Using ignoreboth will also omit repeated lines. Then, hitting the space bar before you enter a command will cause it to not show up in your history file.

# With HISTCONTROL=ignorespace (or =ignoreboth) this line gets written to history
$ mycommand
# But this line does not
$  mycommand

Option 3

If you just want to make it so when you close the terminal the shell exits immediately, you can trap the signal the terminal program sends the shell (xterm, for instance sends SIGHUP then waits for the shell to exit) and make exit without saving the history when it receives this signal. Add this to your ~/.bashrc:

# don't record history when the window is closed
trap 'unset HISTFILE; exit' SIGHUP

Option 4

While some may consider this the "barbarian" approach, sending SIGKILL to your shell's PID will kill your shell right away without the shell being able to do anything such as trap the signal, save history, execute ~/.bash_logout, warn about stopped jobs, or any of that good stuff.

($$ expands to the PID of the shell process executing the command)

kill -9 $$

Answer 2

Your shell's history is saved in the file indicated by the HISTFILE variable. So:

unset HISTFILE

This also applies to zsh, but not to ksh which keeps saving to the file indicated by $HISTFILE when the shell starts (and conversely, you decide to save your history in ksh once you've started the shell).

Answer 3

I'm surprised to see no one has suggested history -c immediately prior to exit. IINM (I'm no expert) that will do nicely.

Answer 4

There are two environment variables that bash uses to determine the history file and how many lines to write to it when the shell exits.

You can throw away your session's history with either of these (set during the session you want to omit from your history file):

HISTFILE=/dev/null

or

HISTSIZE=0

Either of these work fine in Bash on Fedora

Answer 5

Not sure why you care about your command history so much. If you need certain commands often, you might have more fun if you define aliases for them so you can get them back with two keystrokes rather than having to look for them in the history.

Answer 6

1. Eli already gave you the correct answer for Bash which is to set HISTSIZE=0.

2. I would just add the method to do it for GNU screen. Press Ctrl+A (screen escape sequence) followed by :scrollback 0. This will delete scroll-back history. Now you can immediately do :scrollback 15000 to reset scroll-back buffer size.

Answer 7

Here is a safe/natural alternative which should work if you are connected to a unix server via an SSH/telnet client such as PuTTY, which is something that I don't like when it happens, but when you want it to happen, then just let the connection on without interacting with the window until it gets lost when the timeout limit hits, or you can also go ahead and disconnect from internet and try to type something until it disconnects similarly due to network error. This way your commands from that session get lost because you don't properly exit when it would normally save them to history. I don't know if this approach can be applied somehow for a computer that is running unix itself.