Empty Body For Loop Linux Shell
You must specify at least one command in a loop body.
The best comand fo such purposes ia a colon :, commonly used as a no-op shell command.
You could put a no op command inside the loop like true or false (do nothing successfully or unsuccessfully respectively).
This will be a tight loop and will burn CPU. Unless you want to warm up your computer on a cold morning, you can simply say i=1000000 and have the same effect as the loop.
What is it that you're trying to achieve?