Create a zombie that exists even after parent dies.........

saanchi · 02-22-2008, 07:09 AM

I want to create a zombie process that exists even after parent dies. But the problem is that as soon as the parent dies init adopts the zombie process and so it do not exists . could anyone suggest some method that could make me write a c program that enable me see a zombie process after parent exits..............

cicorino · 02-22-2008, 08:30 AM

I'm not expert, anyway maybe you're trying to fake what the 'nohup' does, so I think that you just need to write a signal handler that ignores SIGHUP inside the code of your zombie...or you can use system( "nohup yourZombieExecutable") to run it from the parent.

Telemachos · 02-22-2008, 09:26 AM

I can't answer your question, but I have to say it's on my all-time list of great titles for a post.

ta0kira · 02-22-2008, 10:29 AM

Don't have anything useful either, but if you do figure it out I suggest calling the keeper if the zombies a "Zombie Monger."
ta0kira

osor · 02-22-2008, 11:07 AM

Yes, you will have to ignore SIGHUP and probably close the standard file descriptors. Take a look at man 3 daemon.

saanchi · 02-22-2008, 01:46 PM

ignoring SIGHUP didn't help............it is still being adopted by init ...is there any method by which i could change the parent of any process?

osor · 02-22-2008, 02:09 PM

Quote:

Originally Posted by saanchi

ignoring SIGHUP didn't help............it is still being adopted by init

I thought the goal was to have init (or whatever process is the parent’s parent) adopt the process in question (and the process itself not having exited).

Init will (or should) always wait for the adopted children, so you will never have a “zombie” process which is the child of init (i.e., if the process has already exited, and was previously a zombie since its parent was not waiting for it, and its parent dies, then the zombie will die as well). That’s one of the purposes of init.

ta0kira · 02-22-2008, 04:30 PM

What will the zombie do for you (labor, eating people)? Are you just looking for its exit info? Are these plain forks, or are they forks with execvs? If they're execvs then you could just use a wrapper program that re-forks, execvs, then waitpids and exports the exit info. The wrapper process will stick around even after the parent exits, thereby preserving the defunct process in the table if you want it to wait a long time before the waitpid.
ta0kira

PS Even if it doesn't execv, you can still add an additional fork that does the waitpid after a lengthy delay.

AnanthaP · 02-23-2008, 06:10 AM

I thought that if you end a comand with ampersand, it gets detached from he parent. Isn't that all you really need to do?

Through a C program, I would simply "system or exec or some equivalent".

End

ta0kira · 02-23-2008, 02:47 PM

No, & gives you a process group that doesn't have control of the terminal through tcsetpgrp. It still belongs to the parent unless it calls setsid (normally requires an additional fork if the parent is the shell.) You need setsid to break away from the parent, which can be done using the setsid shell command or system call. When you fg a process, all that does is have the shell give it terminal control with tcsetpgrp.
ta0kira