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72 lines
2.0 KiB
Markdown
72 lines
2.0 KiB
Markdown
# Kill a background job without a message
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\-\-\-- dataentry snipplet \-\-\-- snipplet_tags: kill, process
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management, jobs LastUpdate_dt: 2010-07-31 Contributors: Jan Schampera
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type: snipplet
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------------------------------------------------------------------------
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When you start background jobs from within a script (non-interactive
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shell) and kill it afterwards, you will get a message from the shell
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that the process was terminated.
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Example:
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#!/bin/bash
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# example background process
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sleep 300 &
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# get the PID
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BG_PID=$!
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# kill it, hard and mercyless
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kill -9 $BG_PID
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echo "Yes, we killed it"
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You will get something like this:
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$ ./bg_kill1.sh
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./bg_kill1.sh: line 11: 3413 Killed sleep 300
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Yes, we killed it
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This is more or less a normal message. And it can\'t be easily
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redirected since it\'s the shell itself that yells this message, not the
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command `kill` or something else. You would have to redirect the whole
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script\'s output.
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It\'s also useless to temporarily redirect `stderr` when you call the
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`kill` command, since the successful termination of the job, the
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termination of the `kill` command and the message from the shell may not
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happen at the same time. And a blind `sleep` after the `kill` would be
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just a workaround.
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The solution is relatively easy: The shell spits that message because it
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controls the background job, and when it terminates, the shell will tell
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you whenever possible. Now you just need to tell your shell that it is
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no longer responsible for that background process. This is done by the
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`disown` command, which can take an internal shell job number (like
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`%1`) or a process ID as argument.
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#!/bin/bash
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# example background process
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sleep 300 &
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# get the PID
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BG_PID=$!
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### HERE, YOU TELL THE SHELL TO NOT CARE ANY MORE ###
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disown $BG_PID
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###
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# kill it, hard and mercyless, now without a trace
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kill -9 $BG_PID
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echo "Yes, we killed it"
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That way, you can run and kill background processes without disturbing
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messages.
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