[Linux 常見問題] Best way to kill all child processes

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Question
I want to kill a whole process tree. What is the best way to do this using any common scripting languages? I am looking for a simple solution.

How-To
You don't say if the tree you want to kill is a single process group. (This is often the case if the tree is the result of forking from a server start or a shell command line.) You can discover process groups using GNU ps as follows:

# ps x -o "%p %r %y %x %c "

If it is a process group you want to kill, just use the kill(1) command but instead of giving it a process number, give it the negation of the group number. For example to kill every process in group 5112, use kill -TERM -- -5112. Consider below demonstration shell script which help us to understand how it works more clear.
- test_sleep.sh

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1. #!/bin/sh  
2. echo "Sleep 10 minutes"  
3. sleep 600  

- test.sh

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1. #!/bin/sh  
2.   
3. echo "Sleep 1"  
4. ./test_sleep.sh &  
5. S1=$!  
6. echo "Sleep 2"  
7. ./test_sleep.sh &  
8. S2=$!  
9. wait $S1 $S2  

Let's execute test.sh:

# ./test.sh &
[1] 79863

# ps x -o "%p %r %y %x %c"
...
79863 79863 pts/2 00:00:00 test.sh
79864 79863 pts/2 00:00:00 test_sleep.sh
79865 79863 pts/2 00:00:00 test_sleep.sh
79866 79863 pts/2 00:00:00 sleep
79867 79863 pts/2 00:00:00 sleep
...

So we can try to list process tree:

# ps auxf

To kill test.sh and all its child process(s), do this way:

# kill -TERM -- -79863
[1]+ Terminated ./test.sh

// Make sure the test.sh and test_sleep.sh have been killed
# ps aux | grep test | grep -v grep