Basic Usage

The clear command is one of the simplest yet most frequently used commands in Linux. Its primary function is to clean up your terminal screen, providing a fresh workspace.

clear

Command Syntax and Options

While the basic clear command is straightforward, it comes with several useful options:

• clear -x: Clears screen but doesn’t reposition the cursor
• clear -V: Displays version information
• clear -h: Shows help message

Keyboard Shortcuts

Instead of typing clear, you can use these time-saving keyboard shortcuts:

• Ctrl + L: Clears the screen (equivalent to the clear command)
• Ctrl + U: Clears the current line
• Ctrl + K: Clears from cursor to end of line

Basic Usage

The history command displays a list of previously executed commands with their line numbers:

history

Viewing Command History

To view a specific number of recent commands:

history 10  # Shows last 10 commands

History File Location

By default, bash stores command history in:

~/.bash_history

History Size Configuration

You can configure history size by modifying these variables in ~/.bashrc:

HISTSIZE=1000       # Number of commands stored in memory
HISTFILESIZE=2000   # Number of commands stored in history file

Search Through History

To search through your command history:

• Ctrl + R: Reverse search through history
• Type your search term
• Press Ctrl + R again to cycle through matches

Execute Previous Commands

Several methods to execute previous commands:

!!         # Executes the last command
!n         # Executes command number n from history
!-n        # Executes nth command from the end
!string    # Executes most recent command starting with "string"

History Expansion

Use history expansion to modify previous commands:

^old^new   # Replaces first occurrence of "old" with "new" in previous command
!!:s/old/new   # Same as above but with different syntax

Clearing History

To clear your command history:

history -c    # Clears current session history
history -w    # Writes current history to ~/.bash_history
rm ~/.bash_history    # Deletes entire history file

Preventing Commands from Being Recorded

To prevent recording sensitive commands:

export HISTCONTROL=ignorespace    # Commands starting with space aren't recorded
export HISTIGNORE="ls:pwd:clear"  # Ignore specific commands

Your Turn!

Try this practical exercise:

Problem: Create a script that clears the terminal and displays only the last 5 commands from history.

Solution:

#!/bin/bash
clear
history 5