When you start background jobs from within a script (non-interactive shell) and kill it afterwards, you will get a message from the shell that the process was terminated.
Example:
#!/bin/bash # example background process sleep 300 & # get the PID BG_PID=$! # kill it, hard and mercyless kill -9 $BG_PID echo "Yes, we killed it"
You will get something like this:
$ ./bg_kill1.sh ./bg_kill1.sh: line 11: 3413 Killed sleep 300 Yes, we killed it
This is more or less a normal message. And it can't be easily redirected since it's the shell itself that yells this message, not the command kill or something else. You would have to redirect the whole script's output.
It's also useless to temporarily redirect stderr when you call the kill command, since the successful termination of the job, the termination of the kill command and the message from the shell may not happen at the same time. And a blind sleep after the kill would be just a workaround.
The solution is relatively easy: The shell spits that message because it controls the background job, and when it terminates, the shell will tell you whenever possible. Now you just need to tell your shell that it is no longer responsible for that background process. This is done by the disown command, which can take an internal shell job number (like %1) or a process ID as argument.
#!/bin/bash # example background process sleep 300 & # get the PID BG_PID=$! ### HERE, YOU TELL THE SHELL TO NOT CARE ANY MORE ### disown $BG_PID ### # kill it, hard and mercyless, now without a trace kill -9 $BG_PID echo "Yes, we killed it"
That way, you can run and kill background processes without disturbing messages.