Limit process to one instance.

[mixtape]

What is a good way to limit a process to a single instance. As in attempting to start another process while one is already running it could detect this..?

I'm looking for something un-obvious like checking the process list.

[sitnspinlock]

not checking the process list makes it sound as if you don't want it hacked? ;p

you have a great deal of options but not many that are going to stump a veteran. here are some i can think of at the moment:

try a named synchronization object like a mutex or event. maybe even a section object, those seem to be popular methods.

[DarkLinux]

Everything can be solved with a rootkit . If you are looking for a quick fix that will work its not going to be easy. I have seen some software you can buy that will do the trick with drivers.

[Frosttall]

Everything can be solved with a rootkit . If you are looking for a quick fix that will work its not going to be easy. I have seen some software you can buy that will do the trick with drivers.

Dude you try to shoot with a cannon on flies.

Regex is the best mentioned method so far and very easy to implement. Of course does the method depend on the language you're using, so please tell us its name

[abuckau907]

on start-up, check if process is already running, and if so, exit current process?

main () {
_allProcesses = GetAllRunningProcesses();
if _allProcesses.Contains (myAppName)
Application.Exit();
end if
}

edit: once your process has started, there should be 2 copies of 'myAppName' running -- check for .Contains() twice and exit on that ?

[Kanyle]

Use a mutex

[Cypher]

The common solution is to use a named mutex. Though like everdox said, it sounds like you're looking for something a little more 'stealthy'... Perhaps you could tell us why it needs to be 'un-obvious'?

[abuckau907]

What if they change the name of the program and run it.... Do you think your method would work?

Your question is rhetorical, you're basically saying "You're Wrong."

You're right. I assumed* the program name wouldn't change, because, most don't. If that had been mentioned in the problem, my answer would have been different.

[abuckau907]

What is a good way to limit a process to a single instance. As in attempting to start another process while one is already running it could detect this..?
I'm looking for something un-obvious like checking the process list.

Checking the task manager - any reason you mention doing it this way? It's unobvious, but for a reason - why do it?
process1
process1' <--second occurrence

You say "could it detect this"<-- so you want process1 to 'detect' that process1' is loading/starting up, and kill it ? That's the hard way? Instead make process1' check if process1 is running, and if so, cancel loading. This is the 'usual' way to do it. Unless you have a specific reason to not do it this way? Use regex for string comparison if you want*

example in vb.net

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Dim _allProcesses() As Process = Process.GetProcesses()
        Dim _myAppName As String = Process.GetCurrentProcess.ProcessName
        Dim _foundOnce As Boolean = False
        For Each pp As Process In _allProcesses
            If pp.ProcessName = _myappname Then
                If _foundOnce = False Then
                    'first occurance
                    _foundOnce = True
                Else
                            Me.Exit() ''Application.Exit()
                End If
            End If
        Next
        '' If you get here, there was no 2nd copy found.
        '' Continue as normal.
        '' ...
    End Sub

*this assumes the process name is constant. If yours isn't, please give more project details and I'll try to update the demo.
*if you're not on .Net you might have to code some of the Process() functions yourself - do you have a specific project/language in mind?

c#

        private void Form1_Load(object sender, EventArgs e)
        {
            Process[] _allProcesses = Process.GetProcesses();
            string _myAppName = Process.GetCurrentProcess().ProcessName; //.exe's filename
            bool _foundOnce = false;
            foreach (Process pp in _allProcesses)
            {
                if (pp.ProcessName == _myAppName)
                {
                if (!_foundOnce)
                    _foundOnce = true;
                else
                    this.Close(); //auto exit, no warning to user.
                }
            }
            //if you get here, this is the only copy running. Continue as normal.
            //..
        }

[abuckau907]

edit: removed flame

[namreeb]

Anyone else second that? I'll leave if I'm not wanted...


BTW, he didn't say hide it from the task manager! ..he meant "pull the list of running processes from taskmanager.exe." --which is how the ppl are doing it in auto-it here. (I smell non-programmer) :F

He is correct that few people here use VB, but not that you should leave. But your code may be skipped by most people (I didn't even read it, myself). Nothing personal.

[abuckau907]

@namreeb: ok, not what I wanted to hear ofc, but thnx. Not taken, I wrote it for mixtape, not you --in my first post, i had a quazi-c pseudocode..i should have taken the extra 2 seconds to replace end if w/ } and wrap the if in ( )'s. I'll consider that next time I post code.

[abuckau907]

edit: removed flame

[abuckau907]

edit: removed flame

[abuckau907]

@dark
[I assume] he wasn't asking how to hide it from the task manager, or anything else hacker related?
It's still back there on page 1,show me where it says he's trying to hide his process from the task manager? Or anything else 'hacker-ish.' If he had, my answer would have reflected that. --He just needs basic programming help! "unobvious" != "anti-hacker" --maybe* that is what he meant, but it's not really clearly defined in the post.
My method works for what he asked for.. Your comment was rude and unwarranted. Just because YOU won't read it, doesn't mean the user who asked the question won't read it to help learn some core concept.


edit: massive edits /flames removed