That's a very practical question!
If the directory you are currently in is empty, running the ls command will simply produce no output.
This means your terminal prompt will return immediately, as if nothing happened. It's not an error; it just indicates that there are no files or subdirectories to list in that specific location.
For example:
labex@labex-vm:~/project $ ls
labex@labex-vm:~/project $In the example above, after typing ls, the next line is just a new prompt, showing that the project directory is empty.
Does that clarify it for you?
