Help about Ctrl-Z and Ctrl-Y(urgent)

Greg KH greg at
Wed Feb 17 11:22:51 EST 2016

On Wed, Feb 17, 2016 at 03:52:45PM +0800, 慕冬亮 wrote:
> Hi everyone,
>     Unix systems support a large number of special characters that
> receive special processing by the OS. One such character is the
> “suspend” character (ctrl-Z by default), that causes a SIGTSTP signal
> to be sent to the application process. The default action for the
> signal is to suspend execution of the process. The system responds to
> the suspend character (by sending the signal) as soon as possible
> after it is typed in. In older Unix systems there was another special
> character known as the “delayed suspend” character (ctrl-Y by default)
> that had the same effect as the suspend character, except that the
> signal is sent when the application process consumes the character,
> rather than right away. (That this feature is no longer supported is
> perhaps some indication of how useful it was ...) The suspend and the
> delayed-suspend characters have the effect, when they are processed,
> of deleting all characters currently waiting to be read by the user
> application that arrived before them. Explain, how both special
> characters are implemented?

That sounds like a homework question, why exactly do you need/want to
know this, and what have you done already to try to figure it out

greg k-h

More information about the Kernelnewbies mailing list