When ctrl-c Is Not Enough
Situation
If you’ve been stuck in a terminal where ctrl-c didn’t seem to work
> bash sig-catcher
loop 1
loop 2
loop 3
^C
loop 4
loop 5
^C^C^C^C
loop 6
loop 7
loop 8
# it keeps going ...
you know how frustrating it can be. 🤬
Try ctrl-\
Think of ctrl-\ 1 as a “harder” ctrl-c
> bash sig-catcher
loop 1
loop 2
loop 3
^\sig-catcher: line 5: 38922 Done
It doesn’t always work, but it’s worth trying.
Details
Here’s the script that I used above, to experiment with:
trap '' INT TERM EXIT
seq 1 1000 | while read -r i; do
echo "loop $i"
sleep 1
doneWhat you need to know:
- empty trap –
trap ''– will ignore the listed signals:INT TERM EXIT ctrl-cgenerates aINT, now caught and ignored byTRAP
In man kill, there’s a useful list:
Some of the more commonly used signals:
1 HUP (hang up)
2 INT (interrupt)
3 QUIT (quit)
6 ABRT (abort)
9 KILL (non-catchable, non-ignorable kill)
14 ALRM (alarm clock)
15 TERM (software termination signal)
For context:
- a regular
killcommand sends a:15 / TERM: - a
kill -9command sends a:9 / KILL ctrl-csends a:2 / INTctrl-\sends a:3 / QUIT
And how do we know how ctrl-c and ctrl-\ are hooked up?
> stty -e ~
speed 38400 baud; 40 rows; 140 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 iutf8
-ignbrk brkint -inpck -ignpar -parmrk
oflags: opost onlcr -oxtabs -onocr -onlret
cflags: cread cs8 -parenb -parodd hupcl -clocal -cstopb -crtscts -dsrflow
-dtrflow -mdmbuf
discard dsusp eof eol eol2 erase intr kill lnext
^O ^Y ^D <undef> <undef> ^? ^C ^U ^V
min quit reprint start status stop susp time werase
1 ^\ ^R ^Q ^T ^S ^Z 0 ^W
Find intr and quit with their ctrl (^) bindings
No kill -9 binding?
I thought there might be harder and harder kill bindings, but apparently not.
If you need kill -9, you could bind it but there are no defaults.
-
ctrl-backslash↩