Shell Trick: Saving and Executing Partially Entered Commands Later

Have you ever realized while typing a long, tedious command in the shell that you should have executed another command first? This probably happens quite often, especially for those of you who love one-liner scripts. In such situations, do you reluctantly delete the text you were typing, run the other command, and then retype the original one? Or do you cut the string and paste it later?

Here is a small trick to temporarily save the command you are typing and execute it later. Where do you save it? In your shell history. Specifically, the method is: "move to the beginning of the command, type '#', and press Enter; then, after finishing the other task, find it in your history, remove the '#', and execute it." Here is an example:

1. You type as far as awk '{<long one-liner>}' <input.data > output.data and realize, "Wait, I haven't generated input.data yet!"
2. Move to the beginning of the line, type "#", and press Enter. Since it's treated as a comment, nothing is executed, but it remains in your history (with the "#").
3. Run the command to generate input.data. For example, make input.data.
4. Scroll through your history using the "↑" key or similar. You will find #awk '{<long one-liner>}' <input.data > output.data.
5. Move to the beginning of the line, delete the "#", and press Enter.
6. It succeeds because input.data now exists.

It's not like you're using a hidden feature of the shell or terminal; it's a simple trick once you know it. However, since quite a few people around me didn't know it, I decided to share it here. That's all.