Graceful way to kill process

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After my bash script is done with the selenium server, the script kills it like this:

kill `ps -ef | grep selenium | awk '{ print $2 }'`

While this works and it does kill the selenium script, it also tries to kill the process for grep selenium So by the time that process number gets back to the kill command, the process is gone, so it ends up generating an error message. (In other words: it ends up killing two processes, one of them is the real selenium server, the other is a fleeting process that is a side-effect of how I'm doing this command.)

Is there a more graceful way to kill the process, that doesn't have this unintended side-effect?

(FWIW one idea I had: this same script starts up selenium earlier in the script, so maybe if there was a way I could capture the PID when I start up selenium, I could just keep that and kill it directly, instead of grepping for the process ID. The problem is, I don't know how to get that PID, how to use a variable to keep it and how to reference it later in the script. But is that a better way to go about it?)

Best Answer

Try to use pkill selenium if neither this, nor one of the others work you can keep using your method with another pipe sequence such as

kill `ps -ef|grep -i selenium| grep -v grep| awk '{print $2}'`

Related Solutions

Shell – How to kill a particular thread of a process

Threads are an integral part of the process and cannot be killed outside it. There is the pthread_kill function but it only applies in the context of the thread itself. From the docs at the link:

Note that pthread_kill() only causes the signal to be handled in the context of the given thread; the signal action (termination or stopping) affects the process as a whole.

Process – How to Kill Both Process and Subprocess

There is a standard method, if the programs cooperate. Run kill -- -42 where 42 is the pid of the parent process. This sends a signal to all the processes in the process group lead by process 42 (the minus sign before the pid means process group).

Normally, if you run your python script from a shell prompt and it simply forks gnuchess, the two processes should remain in the same process group. But this doesn't seem to be the case, since Ctrl+C sends SIGINT to the whole foreground process group.

Gnuchess might be in its own process group because it made itself a session leader (but I don't know why it would do this), or because you've double-forked it (python forks a shell which forks gnuchess). A double fork is probably avoidable, but I can't tell you how without seeing your code.

A reasonably reliable and POSIX-compliant way of finding the pid of the gnuchess process is

gnuchess_pids=$(ps -A -o pid= -o cmd= | awk '$2 ~ /(^|\/)gnuchess$/ {print $1}')

Specific unix variants may have better ways of achieving this, such as pgrep.

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