What is Bash History? How to Review It?

If you’ve ever worked with a Linux command-line interface (CLI), you may have wondered exactly which commands you ran while working. Fortunately, a bash history file that keeps track of every command a specific user has typed into the system will help you locate the commands you used. By going over this list, you can diagnose input issues or errors made during command-line activities. This post will teach you how to review bash histories and why the data they include is important.

What is Bash History?

Bash history is the history of commands that have been issued in Bash. The term “Bourne Again Shell,” or “Bash,” refers to a particular kind of user interface or shell that allows users to communicate directly with computer operating systems. Originally designed for Unix systems, this shell is still in use today on the majority of cutting-edge Linux operating systems. Run in Bash, a command is called a bash command. Each of these commands is saved in the bash history and may be examined in a list format using a straightforward Linux function.

Ways to Review Bash History

You can review your bash history using the following command:

history

With this command you will get a numbered list of all past commands entered into the system, in sequential order.

You can expand the amount of commands stored in the bash history, by modifying the .bashrc file. This file displays the operating style of a given user’s bash profile, including the way its bash history is stored. In this file, bash history is stored depending on two parameters.

The first parameter is:

HISTFILESIZE

It dictates the total number of commands stored in the history file.

The second parameter is:

HISTSIZE

It dictates the number of commands stored in a given session. When you increase these values in the .bashrc file, the number of commands stored in the bash history can be increased too.

After having a list of previously-issued commands, they can be called using the number assigned in the history. For example, if you want to rerun the command listed in the history as entry 20, you can call that command as follows:

!20

With this, the command that is associated with the 20th entry on the bash history list will run. Users can simplify the repetitive command-line operations.

The bash history is by default stored at the end of a bash session. During the multiple concurrent sessions, the bash histories may lead to overwriting each other and so only the last connected session will be saved in the history. To resolve this issue, set the bash histories to append, rather than overwrite with the following command:

shopt -s histappend

When you do it correctly, bash histories should be appended to the file for all sessions, even during the concurrent bash sessions.

For clearing the bash history for security reasons, use the following command:

history -c

With this, all commands from your bash history will get cleared permanently. Remember you can’t recover the deleted histories.

It’s evident from the aforementioned examples that you can review bash histories with a few straightforward commands. Because of these features, bash histories are now an essential component of any Linux workflow or troubleshooting procedure.