The Job Execution Control uses SIGKILL when cancelling a started job.
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The Job Execution Control set a new process group when it starts a job so that all of processes can exist in a single process group.
When the job is canceled, a signal (SIGKILL) is sent to all of the processes in the set process group. For this reason, if setpgrp(2) is executed in the processes generated from the job and the process group is changed, the signal (SIGKILL) is not sent to the processes in the modified process group even if the job is canceled.
