0

I want to kill a process and its son process with trap command:

vim   waiting.sh 
trap "kill $$" EXIT
sleep 10000

Now run it in background:

debian@debian:~$  bash   waiting.sh  &
[1] 29590

Have a look at all processes

debian@debian:~$  ps aux | grep '[w]aiting.sh'
debian     29590  0.0  0.0  14556  3164 pts/1    S    16:16   0:00 bash waiting.sh
debian@debian:~$  ps aux | grep '[s]leep'
debian     29591  0.0  0.0  13104   508 pts/1    S    16:16   0:00 sleep 10000

Press ctrl+c to trigger the trap:

debian@debian:~$  ^C
debian@debian:~$  ps aux | grep '[w]aiting.sh'
debian     29590  0.0  0.0  14556  3164 pts/1    S    16:16   0:00 bash waiting.sh
debian@debian:~$  ps aux | grep '[s]leep'
debian     29591  0.0  0.0  13104   508 pts/1    S    16:16   0:00 sleep 10000

How can kill all the processes with trap?
To make my request more concrete,show my os and desktop environment.

debian@debian:~$  uname -a
Linux debian 5.10.0-11-amd64 #1 SMP Debian 5.10.92-2 (2022-02-28) x86_64 GNU/Linux
debian@debian:~$  dpkg -l lxde
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name           Version      Architecture Description
+++-==============-============-============-=================================
ii  lxde           11           all          metapackage for LXDE
debian@debian:~$  dpkg -l openbox
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name           Version         Architecture Description
+++-==============-===============-============-===============================>
ii  openbox        3.6.1-9+deb11u1 amd64        standards-compliant, fast, ligh

I bind hotkey with voice capture,whenever listen to the music playing on my favorite website,click ctrl+shift+r,the bash script /usr/hotkey/ch.sh called ,ffmpeg running on the background,music captured,i want to finish the music capture when to click ctrl+c,my script failed.

  vim  $HOME/.config/openbox/lxde-rc.xml
  <!-- Keybindings for recording voice playing on sound card-->
    <keybind key="C-S-r">
      <action name="Execute">
      <command>bash /usr/hotkey/cr.sh</command>
      </action>
    </keybind>

  cat  /usr/hotkey/cr.sh
  pid=$$
  trap  " pkill -P $pid;kill $pid " SIGINT
  if [[ -f "/tmp/out.mkv" ]];then  rm -f "/tmp/out.mkv";fi
  voice='alsa_output.pci-0000_09_00.6.analog-stereo.monitor'
  ffmpeg -f pulse -i $voice /tmp/out.mkv

I have tried many kinds of trap format, never done.In order to kill ffmpeg,open a terminal and issue commands:

ps aux |grep [f]fmpeg #get ffmpeg's pid
kill pid_number       #close the process

So i want to improve the code,to kill the process triggered by ctrl+shift+r with more samrt way.

showkey
  • 482
  • 42
  • 140
  • 295
  • if you send bash to background with & the ^C is processed by your current bash, not the one with the trap. – criztovyl May 07 '22 at 08:17
  • Another way instead of trap , to kill the `waiting.sh` process running in the background when ctrl+c is typing ? – showkey May 07 '22 at 08:21
  • yes, set a trap in the "current" bash: `trap "kill %1" INT`, `bash waiting.sh &`. If you then press Ctrl-C the first process in background (`%1`) will be sent the `SIGTERM` signal (the default signal `kill` sends). – criztovyl May 07 '22 at 08:33
  • I do as you say,it can't work. – showkey May 07 '22 at 08:38
  • please expand the question how it does not work as expected. – criztovyl May 07 '22 at 08:41

3 Answers3

3

From the extended context you provided the first thing that comes to my mind is using a PID-file and a companion command.

Something like this:

# cr.sh
ffmpeg ... &
# note down pid
echo $! >/tmp/cr.pid

# cr-stop.sh
kill $(cat /tmp/cr.pid)

then you should be able to use cr-stop.sh to stop ffmpeg.

criztovyl
  • 761
  • 5
  • 21
  • I have given wrong bonus ,key binding can't take effect in daemon process trigger by hotkey in lxde-rc.xml,solve the issue with your method instead of others. – showkey May 10 '22 at 07:15
-1

try to use trap "pkill -P $$" SIGINT

SIGINT signal from ctrl+c and on execution of pkill command all the related processes will be killed.

Sunil
  • 84
  • 3
  • Please try on your pc,as my try ,no use for `trap "pkill -P $$" SIGINT` to kill the process itself and its realted process . – showkey May 04 '22 at 14:42
-1

If all you wanted to do is kill ffmpeg process, can you just do :

bind -x '"'$(tput kf5)'":"pkill ffmpeg"'

then in the terminal, you just hit F5 to kill ffmpeg process.

If you want to kill the cr.sh, then you can do

bind -x '"'$(tput kf5)'":"pkill /usr/hotkey/cr.sh"'

and put in cr.sh

if [[ -f "/tmp/out.mkv" ]];then  rm -f "/tmp/out.mkv";fi
voice='alsa_output.pci-0000_09_00.6.analog-stereo.monitor'
ffmpeg -f pulse -i $voice /tmp/out.mkv
Philippe
  • 20,025
  • 2
  • 23
  • 32
  • The bind action is so deeply related with concrete function ,if the function in `cr.sh` is others ,instead of `ffmpeg`,rewrite the bind statement,not a good practice. – showkey May 07 '22 at 12:13
  • New issue related to this post,https://stackoverflow.com/questions/72153177/why-bind-x-fput-kf5pkill-ffplay-take-as-same-effect-as-bind-x. – showkey May 07 '22 at 13:56
  • `pid=$$;trap " pkill -P $pid;kill $pid " EXIT` is no need to stay ,they can't work,it is better to remove them in script,please remove them and i give bonus. – showkey May 08 '22 at 06:58