I saw the Old Discussions at forum, it has no meaning...
https://groups.google.com/forum/m/#!topic/tasker/DeEHhw2emao
Today I runned a shell script about "Getevent" -same as above discussions- with 5 sec of timeout. But it doesn't timeout.
And it worked on my device earlier, but after several updates, some months, today, it doesn't.
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I performed above as task, give a stop action to that task, it doesn't stop itself.
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So, the result is... you had an mistake with root permission.
A shell script action with root permission can't be controlled by tasker, th owner app.
It just can be excuted by, but