How to use the command 'clear' (with examples)
The clear command is a basic utility found in Unix-like operating systems that allows you to clear the contents displayed on a terminal screen. This command is used to refresh the terminal window by wiping it clean, making it easier to view new output, especially when you’ve scrolled through a lot of text or executed multiple commands. The screen is cleared without closing the terminal session, simply providing a clean slate for further processing or commands. Below, we explore different use cases of the clear command and its options.
Use case 1: Clear the screen
Code:
clear
Motivation:
In a busy terminal session, your screen can quickly become cluttered with command outputs, system messages, and other text. This can make it challenging to focus on the task at hand or identify the results of recent commands. By using the clear command, you can instantly wipe the screen clean, providing a distraction-free workspace. This is particularly useful during troubleshooting or when executing multiple scripts, allowing you to see only the most relevant information on the screen without any background noise from previous commands.
Explanation:
The clear command, when executed without any arguments, refreshes the terminal screen by removing all previously displayed text. It acts as if you have just opened a new terminal session, although existing processes and the terminal’s scrollback buffer remain unaffected.
Example Output:
After running the command, the terminal appears completely empty, with only the cursor present at the top left corner ready for input.
Use case 2: Clear the screen but keep the terminal’s scrollback buffer
Code:
clear -x
Motivation:
Sometimes, it’s useful to clear the current view of the terminal screen while still being able to access the history of previous commands and outputs. This is common when analyzing logs or reviewing long scrollbacks that might have minor interruptions. By retaining the scrollback buffer, you ensure that all the past output remains accessible for reference without it being re-rendered on the main screen.
Explanation:
The -x option allows you to clear only the visible portion of the terminal screen, while keeping the scrollback buffer intact. This is akin to pressing Ctrl + L in many Shell environments, like Bash. This option is tremendously beneficial to users who may want to quickly declutter their screen but still have the ability to scroll back through terminal history if needed.
Example Output:
The terminal screen is cleared, similar to the basic clear command, but you have the flexibility to scroll back up to view previously executed commands and their outputs.
Use case 3: Indicate the type of terminal to clean
Code:
clear -T type_of_terminal
Motivation:
In many environments, especially those involving remote systems or diverse terminal emulators, specifying the terminal type can be crucial for ensuring that operations are executed appropriately. Different terminals can have varying capabilities and handling, and defining the terminal type ensures compatibility and expected behavior when clearing the display.
Explanation:
The -T option allows you to explicitly specify the type of terminal you are using with the clear command. By default, it uses the value set in the environment variable TERM. By providing a terminal type, you inform the command precisely how to clear the screen for that specific terminal emulator or system type, which is particularly valuable in scripts or when working on systems with multiple terminal types.
Example Output:
Clears the terminal screen according to the capabilities tied to the specific terminal type argument you provided, ensuring no discrepancies in behavior across different systems or interfaces.
Use case 4: Display the version of ncurses used by clear
Code:
clear -V
Motivation:
Understanding the version of the software and libraries your system relies on is critical for maintenance, troubleshooting, and ensuring compatibility with certain applications or scripts. The ncurses library provides functions to write text-based user interfaces in a terminal-independent manner, and knowing its version can help developers and system administrators manage dependencies and cross-version compatibility efficiently.
Explanation:
The -V option displays the version of the ncurses library that the clear command is using. This can be extremely helpful for debugging or verifying the environment’s setup and is typically part of broader system checks or configuration verifications.
Example Output:
Displays a string similar to ncurses 6.0, indicating the version number of the ncurses library that the clear command is utilizing.
Conclusion:
The clear command is essential for managing terminal visibility and session cleanliness in Unix-like operating systems. By using its various options, you can tailor the functionality to suit your workflow, whether it involves specifying terminal types or keeping scrollback buffers intact. Understanding these use cases enhances productivity and ensures a smooth command-line experience, particularly in environments with mixed-terminal usage or extensive historical command data.
