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16.18. Catching Ctrl-C
16.18.1. Problem
You want to intercept Ctrl-C, which
would otherwise kill your whole program. You'd like to ignore it or
run your own function when the signal is received.
16.18.2. Solution
Set a handler for
SIGINT. Set it to "IGNORE" to
make Ctrl-C have no effect:$SIG{INT} = 'IGNORE';
Or set it to a subroutine of your own devising to respond to Ctrl-C:$SIG{INT} = \&tsktsk;
sub tsktsk {
$SIG{INT} = \&tsktsk; # See ``Writing A Signal Handler''
warn "\aThe long habit of living indisposeth us for dying.\n";
}
16.18.3. Discussion
Ctrl-C isn't directly affecting your program. The terminal driver
processing your keystrokes recognizes the Ctrl-C combination (or
whatever you've set your terminal to recognize as the interrupt
character), and sends a SIGINT to every process in
the foreground process group (foreground job)
for that terminal. The foreground job normally comprises all programs
started from the shell on a single command line, plus any other
programs run by those programs. See Signals in
the Introduction to this chapter for details.The interrupt character isn't the only special character interpreted
by your terminal driver. Type stty
-a to find out your current settings:% stty -a
speed 9600 baud; 38 rows; 80 columns;
lflags: icanon isig iexten echo echoe -echok echoke -echonl echoctl
-echoprt -altwerase -noflsh -tostop -flusho pendin -nokerninfo
-extproc
iflags: -istrip icrnl -inlcr -igncr ixon -ixoff ixany imaxbel -ignbrk
brkint -inpck -ignpar -parmrk
oflags: opost onlcr oxtabs
cflags: cread cs8 -parenb -parodd hupcl -clocal -cstopb -crtscts -dsrflow
-dtrflow -mdmbuf
cchars: discard = ^O; dsusp = ^Y; eof = ^D; eol = <undef;>
eol2 = <undef; erase = ^H; intr = ^C; kill = ^U; lnext = ^V;>
min = 1; quit = ^\; reprint = ^R; start = ^Q; status = <undef;>
stop = ^S; susp = ^Z; time = 0; werase = ^W;
The last section, cchars:, is the list of special
characters. Recipe 15.8 shows you how to
change these from your script without calling the
stty program.
16.18.4. See Also
Your system's stty(1) manpage (if you have one);
Recipe 15.8; Recipe 16.17
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| 16.17. Writing a Signal Handler |  | 16.19. Avoiding Zombie Processes |
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