Injecting Variables into a running Process

Question

Is there a way to inject a variable into a running process without a process listening for RPC requests?

For example if a process was running and using an environment variable, could I change that environment variable at runtime and make the process use the new value?

Are there alternative solutions for dynamically changing variables in a running process? Assume that this process is like a PHP process or a Javascript (node.js) process so I can change the source code... etc.

I think this is similar to passing state or communicating to another process, but I need a really lightweight way of doing so, without going over the network or using libraries or preferably not setting up an RPC server.

Solution does not have to be cross-platform. Prefer Linux.

Any, PHP, JS, Python, Ruby, Erlang, what ever you can think of. — CMCDragonkai, Jun 23 '14 at 05:01
You don't have any idea what programming language this is going to be in? — Robert Harvey, Jun 23 '14 at 05:02
It could be in any. I'm looking for a generic pattern that I can port and understand to any environment I'm working in. — CMCDragonkai, Jun 23 '14 at 05:02
Environment Variables are a Windows concept. Well, you have them in Linux too, but they're not cross-platform AFAIK. — Robert Harvey, Jun 23 '14 at 05:03
@pmverma Node.js process obviously. Environment variables exist in Linux! I've used them before! — CMCDragonkai, Jun 23 '14 at 05:04
We could do this dance all night, but maybe you ought to make your question a bit more specific. Tell us a bit more about the problem you're trying to solve. — Robert Harvey, Jun 23 '14 at 05:04
I don't understand why you want to make this a specific programming language problem. If you must have a language, try PHP then. — CMCDragonkai, Jun 23 '14 at 05:05
Because we're going to attempt to answer your question, and you're going to say "well, that's not quite what I meant," or "I've already tried that, but it didn't work," or "Well, that won't meet my need, because I need to frobnosticate the doomaflatchit at the same time." — Robert Harvey, Jun 23 '14 at 05:06
How is that possible? I'm looking for any solution in any language. If it demonstrates that it resolves the problem of dynamically changing an environment variable in a lightweight manner while the process is running, then it's fine isn't it? — CMCDragonkai, Jun 23 '14 at 05:07
Based on [this question and it's answer](http://stackoverflow.com/questions/3416638/set-environment-variables-in-c), the answer to your question "Is there a way to inject a variable into a running process without a process listening for RPC requests?" appears to be "no." I believe that this is also generally true for Windows. — Robert Harvey, Jun 23 '14 at 05:12
What about shared memory? http://stackoverflow.com/questions/14225010/fastest-technique-to-pass-messages-between-processes-on-linux — CMCDragonkai, Jun 23 '14 at 05:15

score 1 · Answer 1 · answered Sep 20 '16 at 07:46

You can do it it java. Imagine this is your thread class:

public void ThreadClass extends Thread {
Boolean state;

ThreadClass(Boolean b) {
state = b;
    }

public void StopThread() {
state = false;
    }

public void run() {
while(state) { //Do whatever you want here}
    }
}

Now all you have to do is start this thread from your main class:

ThreadClass thread = new ThreadClass(true);
    thread.start();

And if you want to change the value of state, call the StopThread method in the thread like so:

try {
        thread.StopThread();
    } catch (InterruptedException ex) {
        Logger.getLogger(NewClass.class.getName()).log(Level.SEVERE, null, ex);
    }

This will change the state of the Boolean while the thread is running.

This is what I thought you meant since the question was vauge — DavidPrabhu, Sep 20 '16 at 08:13

score 0 · Accepted Answer · edited May 23 '17 at 12:32

0

It appears that local IPC implementations like shared memory is the way to go: Fastest technique to pass messages between processes on Linux?

edited May 23 '17 at 12:32

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answered Jun 23 '14 at 06:07

CMCDragonkai

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Injecting Variables into a running Process

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