Roger Oberholtzer wrote:
On Tue, 2008-01-22 at 11:33 -0600, Jeffrey L. Taylor wrote:
I have a program that starts and stops a child process w/ STOP and CONT
signals. Is there a way to do the same for any processes the child forks
(i.e. grandchild, great grandchild, etc.)?
Yes.
original process opens a socket before forking any children,
and pass the socket ID to the child process in the argument
vector.
When the main process forks off a child, it immediately has
the PID of the child process, because the fork(2) returns
the PID of the child process to the parent. With this,
the parent process can start to build a tree (with itself
as root, and all child processes as first-level nodes).
Likewise, Child processes (and grand children, etc), all
know the PID of offspring of the next generation, and if
each one ALSO has the socket number of the original process,
each one can report new offspring to the original process
as soon as fork(2) returns.
If strict "geneology" is required, each reporting process
should send a 2-tuple message consisting of its own PID,
and the child process which it just forked off. (or n-tuple
if additional identifying data is required).
With this information, the parent process can construct
a tree of all "offspring" processes.
Likewise, calling wait(2), using WNOHANG, each generation
of processes can monitor the continued existance of its
children, and report the death of any child process
(say, by reporting a dead child as a negative number,
i.e. -PID) similar to reporting a newly forked child.
Note that this method requires programming in C, C++, or
a similar language capable of calling fork(2) and creating
and manipulating tree-structures.
How's that for someone who hasn't written an application
in C in 18 years?
There is the concept of a process group. Maybe setpgrp/getpgrp will give
a clue? All children, and their children, are part of the same process
group. I think this is really coarse grained in that you can do things
to all members of the process group, not just specific ones. But maybe
you can use this to find who they are. Sorry I cannot say more. I have
not really used this.
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