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--- !ruby/object:RI::MethodDescription
aliases: []
block_params:
comment:
- !ruby/struct:SM::Flow::P
body: Some operating systems retain the status of terminated child processes until the parent collects that status (normally using some variant of <tt>wait()</tt>. If the parent never collects this status, the child stays around as a <em>zombie</em> process. <tt>Process::detach</tt> prevents this by setting up a separate Ruby thread whose sole job is to reap the status of the process <em>pid</em> when it terminates. Use <tt>detach</tt> only when you do not intent to explicitly wait for the child to terminate. <tt>detach</tt> only checks the status periodically (currently once each second).
- !ruby/struct:SM::Flow::P
body: The waiting thread returns the exit status of the detached process when it terminates, so you can use <tt>Thread#join</tt> to know the result. If specified <em>pid</em> is not a valid child process ID, the thread returns <tt>nil</tt> immediately.
- !ruby/struct:SM::Flow::P
body: In this first example, we don't reap the first child process, so it appears as a zombie in the process status display.
- !ruby/struct:SM::Flow::VERB
body: " p1 = fork { sleep 0.1 }\n p2 = fork { sleep 0.2 }\n Process.waitpid(p2)\n sleep 2\n system("ps -ho pid,state -p #{p1}")\n"
- !ruby/struct:SM::Flow::P
body: <em>produces:</em>
- !ruby/struct:SM::Flow::VERB
body: " 27389 Z\n"
- !ruby/struct:SM::Flow::P
body: In the next example, <tt>Process::detach</tt> is used to reap the child automatically.
- !ruby/struct:SM::Flow::VERB
body: " p1 = fork { sleep 0.1 }\n p2 = fork { sleep 0.2 }\n Process.detach(p1)\n Process.waitpid(p2)\n sleep 2\n system("ps -ho pid,state -p #{p1}")\n"
- !ruby/struct:SM::Flow::P
body: <em>(produces no output)</em>
full_name: Process::detach
is_singleton: true
name: detach
params: |
Process.detach(pid) => thread
visibility: public