How to Run a Linux Command Without Saving It in History

As a Linux user, you may find yourself needing to run a command that you don’t want to be saved in your shell’s history. This can be useful for a variety of reasons, such as protecting sensitive information or preventing a particular command from being run again accidentally. In this article, we’ll explore several methods for running a Linux command without saving it in history.

Prefix the Command With a Space

One simple method to prevent a command from being saved in history is to prefix it with a space. When a command is preceded by a space, it will not be saved in the shell’s history. Let’s say that we have a command that we want to run without it being saved in history. Here is an example:

$  echo "This command should not be saved in history"

By placing a space before “echo”, the command will not be saved in the shell’s history. This ensures that it will not appear in the history file or be accessible via the up arrow key.

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Use a History Command to Delete the Entry

If you have already run a command and want to remove it from your shell’s history, you can use a history command to delete the entry. This is achieved with the following steps:

1. Use the “history” command to view your shell’s history.
2. Identify the command that you wish to delete.
3. Use the “history -d” command to delete the entry.

Here is an example:

$ history
  1  echo "This command should not be saved in history"
  2  ls
  3  cd ..
$ history -d 1
$ history
  1  ls
  2  cd ..

By using the “history -d” command with the appropriate entry number, the command is deleted from the shell’s history.

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Set the HISTCONTROL Variable

Another way to prevent commands from being saved in your shell’s history is to set the HISTCONTROL variable. This variable controls which commands are saved in the shell’s history. By default, HISTCONTROL is set to “ignoredups”, which means that duplicate commands will not be saved in the history. However, you can change this to “ignorespace” to prevent commands with a leading space from being saved.

Here is an example:

$ export HISTCONTROL=ignorespace
$  echo "This command should not be saved in history"
$ history
  1  ls
  2  cd ..

By exporting the HISTCONTROL variable as “ignorespace”, any command with a leading space will not be saved in the shell’s history.

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Use the “unset” Command

If you want to prevent all commands from being saved in your shell’s history, you can use the “unset” command to unset the HISTFILE and HISTSIZE variables. This is achieved with the following steps:

1. Use the “unset” command to unset the HISTFILE and HISTSIZE variables.
2. Run the command that you do not want to be saved.
3. Use the “history” command to confirm that the shell’s history is empty.

Here is an example:

$ unset HISTFILE HISTSIZE
$ echo "This command should not be saved in history"
$ history

By unsetting the HISTFILE and HISTSIZE variables, no commands will be saved in the shell’s history. Running the command will not cause it to be saved, and the “history” command will show an empty history.

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Use the “history -p” command

This method allows you to execute a command without it being added to your shell’s history.

Here are the steps to use this method:

1. Open your terminal and type history to view your command history. This will display a list of your previously executed commands along with their corresponding command numbers.

$ history
  1  ls
  2  cd Documents/
  3  nano file.txt

2. Identify the command that you want to execute without being saved in your history.

3. Use the history -p command followed by the command that you want to execute without being saved in your history. This will execute the command but it will not be added to your history.

$ history -p "echo 'This command will not be saved in history'"
This command will not be saved in history

4. Check your command history again using history command to confirm that the command was not saved.

$ history
  1  ls
  2  cd Documents/
  3  nano file.txt

As you can see in the example above, the echo command that we executed using the history -p command was not saved in our shell’s history.

It is important to note that this method only prevents the command from being saved in your current shell session’s history. If you open a new terminal window or start a new shell session, the command will not be present in your history as expected. However, if you run the same command again in the same shell session, it will still be saved in the history.

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Conclusion

In this blog post, we have discussed several methods for running Linux commands without saving them in history. These methods include prefixing the command with a space, using a history command to delete the entry, setting the HISTCONTROL variable, using the “unset” command, and using the “history -p” command. Each of these methods has its own advantages and disadvantages, so it is important to choose the appropriate method based on your specific needs.

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