Check if thread is finished in c++11?

Question

I need a way to know if the thread I am running is finished or not. If it is not finished it wait and if it is finished print a successful message.

I don't find a method or something like that in c++11 from library thread. I can't set a global variable because inside thread I am using execvp and it does not return if successful.

Is there any way to do that? A method or flag or anything else.

Edit: To make it clear I want to write a function that checks if thread is finished.

Maybe `join` does what you want? Also, won't execvp replace your *entire* process? — R. Martinho Fernandes, Nov 13 '12 at 11:00
That does not help, I need something like `while (thread not finished){1;} cout <<"thread finished"< — Hamed JML, Nov 13 '12 at 11:05
That's what `join` does (except it won't waste processor time to do nothing)... — R. Martinho Fernandes, Nov 13 '12 at 11:05
I have more than one thread. I don't want to wait until first finish. — Hamed JML, Nov 13 '12 at 11:29
You are giving contradictory requirements ("something like `while (thread not finished){1;}`" and "don't want to wait" are opposites). That makes your stated problem unsolvable. You may want to make the actual requirements more clear if you really want a workable solution. — R. Martinho Fernandes, Nov 13 '12 at 11:32
If you simply want to wait for one thread to execute, then don't use a thread — thecoshman, Nov 13 '12 at 11:37
Keep in mind that such a function can only give you meaningful positives; it will generate false negatives, because a `false` result is outdated the moment it is returned. — R. Martinho Fernandes, Nov 13 '12 at 11:39
Can't you just set a flag `isFinished` and signal a `condition_variable` at the end of the thread? — Gunther Piez, Nov 13 '12 at 12:12
As I am using `execvp` it is not possible. Any way I solve my problem. — Hamed JML, Nov 13 '12 at 12:32

score 6 · Accepted Answer · answered Nov 13 '12 at 11:02

6

You can use C++11 futures and promises:

Futures are a high level mechanism for passing a value between threads, and allow a thread to wait for a result to be available without having to manage the locks directly.

The benefits of futures over using plain threads are:

Future returns a value.
You can wait on a future with a timeout.

Surely, this can be done with plain threads, but why reimplement a wheel with C++11.

answered Nov 13 '12 at 11:02

Maxim Egorushkin

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Call [std::future::wait_until()](http://en.cppreference.com/w/cpp/thread/future/wait_until) with a 0 timeout. – Maxim Egorushkin Nov 13 '12 at 11:36

Check if thread is finished in c++11?

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