reading the exit value of a defunct process

Question

I have a dead process that is now in the defunct state which means that its parent process has not read its exit value. (and it is not going to read it)

I know that the exit value is stored somewhere in the kernel for the parent process to read but, is there a way for me to read that value if I am not the parent process ?

Ideally, I would be able to do this from a shell or an abritrary C/python/your-favorite-language program.

[edit]: This is not a question on how to reap the child or kill it. I do not care if it uses up a slot in the process table. I just want to know what its exit value is. i.e., I would like to read task_struct->exit_code in the kernel.

Mathieu

I think that `init` takes over as parent of all zombies... Not sure though. — Linuxios, Jul 05 '12 at 14:53
No, it takes over only once the parent is dead. This is not my case: the parent is still running but I _know_ that it will not read the exit value — mathieu, Jul 05 '12 at 14:54
Well in solaris it's a trivial matter of using `preap`, don't know about Linux, though — Anya Shenanigans, Jul 05 '12 at 14:55

score 1 · Answer 1 · answered Jul 05 '12 at 14:58

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One thing you might be able to do is to send the parent SIGCHLD, which tells it that a child has died. If the program is of any quality, it will reap the process.

kill -s SIGCHLD parentpid

answered Jul 05 '12 at 14:58

Linuxios

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score 0 · Accepted Answer · answered Jul 05 '12 at 14:56

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No. Attempting to call waitpid() for a process that is not one of the calling process's children will result in ECHILD. You will need to kill the parent process, causing the child to reparent to init, which will subsequently reap it.

answered Jul 05 '12 at 14:56

Ignacio Vazquez-Abrams

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Note that I am not looking into how to real the child. I do not care. I just want to look at the damn exit value. – mathieu Jul 05 '12 at 15:13
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Doing that would require kernel support; no user process has direct access to it except incidentally, e.g. `strace`. – Ignacio Vazquez-Abrams Jul 05 '12 at 15:21

reading the exit value of a defunct process

2 Answers2