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

慕冬亮 mudongliangabcd at
Thu Feb 18 23:59:15 EST 2016

    This question is provided by one of my friends. He only provided
me little information. I didn't know much detail in this part.
    I have searched the relative information on the network. But with
no good result. So I asked for help in mailing list.

2016-02-18 0:22 GMT+08:00 Greg KH <greg at>:
> 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
> yourself?
> greg k-h

My best regards to you.

     No System Is Safe!

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