How do I kill a process which is running in bash - for example, suppose I open a file:

$ gedit file.txt

is there any way within the command prompt to close it? This example is fairly trivial, since I could just close the window, but it seems to come up a bit, particularly when I mistype commands.

Also is there any way to escape an executable which is running? This probably has the same solution, but I thought I'd ask anyway.

Thanks