How can I set a global variable of a Linux process from another process?

Question

I'm creating a fault injection framework, and would like to do something like:

volatile bool doFaultWriteError;

In my code, I can then check the global variable to decide whether to do the fault.

In BSD, I hear you can teach sysctl to set variable in user space processes. Is this possible in Linux? How do I do it?

My current plan is to have a SIGHUP handler that read a "fault configuration" file and then sets globals as appropriate. But if there's already something in Linux that can do this, that would be simpler.

Programming language? http://www.makelinux.net/alp/035 – bartimar Oct 01 '13 at 13:00 — bartimar, Oct 01 '13 at 13:00

score 5 · Accepted Answer · answered Oct 01 '13 at 13:05

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You can use mmap to share a page via a file handler (shm_open) then communicate between two applications.

answered Oct 01 '13 at 13:05

auselen

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score -1 · Answer 2 · edited May 23 '17 at 11:50

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You cannot change the environment of another process, and I would be surprised if you could do that in any UNIX system.

There are some hacks described in this other question: Is there a way to change another process's environment variables? but they are just ugly hacks :)

edited May 23 '17 at 11:50

Community

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answered Oct 01 '13 at 13:03

Martina Ferrari

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The question is to change a _global variable_ in the process-space, and not an environment variable per-se. – Nikhil Oct 01 '13 at 13:05
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Debuggers and dtrace/systemtap let you modify state of another process, so the hooks are there. – Martin C. Martin Oct 01 '13 at 13:25

How can I set a global variable of a Linux process from another process?

2 Answers2