Ctrl+c,ctrl+z,ctrl+d

1, CTRL + C more violent, is to send terminal to the current program, such as you are running a lookup function, files are looking, CTRL + C will force the end of the current process.
2, Ctrl+z is the current program hangs, suspend the implementation of this program, such as you are in the MySQL terminal, need to come out to do some other file operations, and do not want to quit the MySQL terminal (because the next time you have to enter the user name password into, very troublesome), so you can CTRL + Z will suspend MySQL, and then do other operations, and then enter FG return can return, of course, can hang a lot of process to the background, and then the FG plus number will be able to suspend the process back to the foreground. Of course, it is very convenient to switch front and rear with BG and FG commands.
3, Ctrl+d is to send an exit signal, not so strong, like Ctrl + C operation, such as you from administrator root back to your ordinary users can be used.