topic Re: Regarding Control+D & Control+C in Operating System - HP-UX

Regarding Control+D & Control+C

Praveen Motupalle — Tue, 11 Dec 2007 05:27:53 GMT

I need small help to understand how it will works Control-D and Control-C for terminating remote session or any application.

When i press ControlD or ControC which process it will stopor which are the steps will run backend.

Thanks & Regards - Praveen

Re: Regarding Control+D & Control+C

Torsten. — Tue, 11 Dec 2007 07:00:03 GMT

Do you know about signals?

CTRL C = SIGINT

start to read here:

http://en.wikipedia.org/wiki/Signal_%28computing%29

or here

http://docs.hp.com/en/B2355-60105/kill.1.html

Re: Regarding Control+D & Control+C

Dennis Handly — Tue, 11 Dec 2007 10:52:48 GMT

Control-D sets EOF. This is the end of your application's data.
You can get your shell to ignore: set -o ignoreeof
(You will have to use exit to logout.)

Re: Regarding Control+D & Control+C

Laurent Menase — Tue, 11 Dec 2007 14:28:38 GMT

In fact it is processed by your tty.

When you press ^C, and if your tty is configured with ^C set for intr, then it will send a SIGINTR to the forground process.

The mapping of such controls are set via stty

stty -a
# stty -a
speed 9600 baud; line = 0;
rows = 24; columns = 80
min = 4; time = 0;
intr = ^C; quit = ^\; erase = ^H; kill = ^U
eof = ^D; eol = ^@; eol2 ; swtch
stop = ^S; start = ^Q; susp ; dsusp
werase ; lnext
parenb -parodd cs7 -cstopb hupcl -cread -clocal -loblk -crts
-ignbrk brkint ignpar -parmrk -inpck istrip -inlcr -igncr icrnl -iuclc
ixon -ixany ixoff -imaxbel -rtsxoff -ctsxon -ienqak
isig icanon -iexten -xcase echo echoe echok -echonl -noflsh
-echoctl -echoprt -echoke -flusho -pendin
opost -olcuc onlcr -ocrnl -onocr -onlret -ofill -ofdel -tostop tab3

If I want that ^X as kill I just type
stty kill ^X

Then if ^X is pressed it will send a sigkill to the foreground process.

Re: Regarding Control+D & Control+C

A. Clay Stephenson — Tue, 11 Dec 2007 16:32:28 GMT

The most important aspect of this question is that the answer can only be "it depends". How a given process responds to a given signal is entirely up to the process. In fact, (assuming that Cntl-C generates a SIGINT) a Ctrl-C might cause the process to do one behavior at one point and another behavior at another point because the signal handler can be changed while the process is running. The signal handler may be null, in which case the signal is ignored.

Re: Regarding Control+D & Control+C

Dennis Handly — Tue, 11 Dec 2007 22:56:18 GMT

>Clay: The signal handler may be null, in which case the signal is ignored.

Actually you have to use SIG_IGN. SIG_DFL just randomly happens to be 0. :-)