How can I quickly find previous commands I wrote in gnome-terminal?
To quickly find previous commands you wrote in gnome-terminal, you can use the up and down arrow keys. The up arrow key will cycle through previously entered commands in reverse chronological order, while the down arrow key will cycle through them in the opposite direction.

You can also use the history command to see a list of previously entered commands. To quickly find a specific command, you can use the CTRL + R key combination and start typing the command you're looking for. This will initiate a reverse search through the history and display the most recent command that matches what you've typed so far.

Additionally, you can use the grep command to search for specific commands in the history. For example, to find all commands that contain the word example, you can run the following command:

```bash
history | grep example
```

These are just a few ways to find previous commands in gnome-terminal. Experiment with these methods to find the one that works best for you.
Some commands that I typed a long time ago are now out of my history, and I'm sad about that. How do I allow the command history to be longer?
You can increase the length of the command history in gnome-terminal by modifying the value of the HISTSIZE environment variable. Here's how you can do it:

Open the terminal and type the following command: echo $HISTSIZE. This will show you the current value of the HISTSIZE variable.

To increase the length of the command history, set the value of HISTSIZE to a larger number. For example, to set the history length to 1000 commands, type the following command: export HISTSIZE=1000.

To make this change permanent, you need to add the above command to your shell configuration file, such as .bashrc or .bash_profile. To do this, open the file in a text editor and add the following line at the end of the file: export HISTSIZE=1000.

Save the file and close the text editor. Then, close and reopen the terminal, or type source [filename] (replacing [filename] with the name of your shell configuration file, e.g. .bashrc) to apply the changes.

Note: The value of HISTSIZE only affects the number of commands stored in memory, not the number of commands stored in the history file (usually ~/.bash_history). To increase the length of the history file, you can modify the value of the HISTFILESIZE variable in the same way as described above.