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Python and Bash Scripting Adventure 0.1

Optimizing Terminal Scripts with It

When I open the terminal, I often have to check and update the system using sudo apt update. I thought this process could be made more efficient, so I started considering creating a script that would automatically perform this update only once each time the terminal is opened.

I planned to write the script in the .bashrc file. The goal was to check if the marker file /tmp/.apt_update_done exists. If it doesn’t, the terminal will run the update and then create the marker file. To ensure this process starts over the next time I open the terminal, the marker file must be deleted every time I exit the terminal.

Combining the Power of Bash and Python

After formulating this idea, I began writing the code. Here’s the basic script I created:

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if [ ! -f /tmp/.apt_update_done ]; then
    sudo apt update
    touch /tmp/.apt_update_done
fi

trap 'rm -f /tmp/.apt_update_done' EXIT
  • if [ ! -f /tmp/.apt_update_done ]; then: This conditional statement checks if the file /tmp/.apt_update_done does not exist.
  • sudo apt update: This command updates the package list on the system.
  • touch /tmp/.apt_update_done: This command creates the marker file that indicates the update has been performed.
  • trap: This is a command to capture a signal or event.
  • trap 'rm -f /tmp/.apt_update_done' EXIT: This captures the exit event from the terminal (EXIT) and deletes the marker file when the terminal is closed.

When to Use trap

trap is typically used in situations where you need to ensure that something is done before a script exits. Some common uses include:

  1. Resource Cleanup: Deleting temporary files, closing database connections, or releasing other resources.
  2. Error Handling: Providing handling for situations when the script does not execute correctly.
  3. Signal Handling: Capturing signals such as SIGINT (which is generated when you press Ctrl+C) to execute specific commands.


However, I wanted to add a little Python touch mwehehe... This was my way of practicing Python. I modified my code to this:

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if [ ! -f /tmp/.apt_update_done ]; then
    python3 -c 'import os; os.system("sudo apt update"); open("/tmp/.apt_update_done", "w").close()'
fi

trap 'python3 -c "import os; os.remove(\'/tmp/.apt_update_done\') if os.path.exists(\'/tmp/.apt_update_done\') else None"' EXIT
  • python3 -c 'import os; os.system("sudo apt update"); open("/tmp/.apt_update_done", "w").close()':

  • Here, we run the command sudo apt update using Python and create the marker file using open. Let’s break this down:

    • python3 -c: Executes the Python code written afterwards.
    • os.system("sudo apt update"): Calls the command sudo apt update from within Python, just like running it in the terminal. This will update the package list on the system.
    • ;: Provides a separator between two statements in Python, allowing us to execute the next command after the previous one completes.
    • open("/tmp/.apt_update_done", "w").close(): Creates the marker file /tmp/.apt_update_done. This writes an empty string to the file, indicating that the update has been performed.

  • trap 'python3 -c "import os; os.remove(\'/tmp/.apt_update_done\') if os.path.exists(\'/tmp/.apt_update_done\') else None"' EXIT:

  • This captures the exit event from the terminal and uses Python to delete the marker file only if it exists. Let’s break this down as well:
    • trap: Captures certain signals that occur, in this case, when the terminal closes (EXIT).
    • python3 -c: Executes the Python code written afterwards when the terminal closes.
    • os.remove(\'/tmp/.apt_update_done\'): Deletes the marker file.
    • if os.path.exists(\'/tmp/.apt_update_done\'): Checks whether the marker file exists before trying to delete it, to avoid errors if the file does not exist.