Category: Usleep example

A microsecond is one millionth of a second. Example 1 usleep example. Edit Report a Bug. Return Values No value is returned.

This was the same on PHP 5. If you're using Windows then you maybe are in trouble with usleep if you really need to use it. The Bernie's microdelay function using fsockopen does not work properly, and the fclose doesn't help much.

usleep example

I don't know if network connections go strange, but I know it does not work since you've made more than - calls to it, so it's not a reliable solution in 'long life' php scripts, or these are the issues of the microdelay function in my PHP and PHP-GTK applications. So I get with this snippet wich works fine for me, you get milliseconds precission but the more important, it works for long-run scripts and of course, it does not waste any CPU cycles.

Note that this function has an overhead! Script take about 70 microseconds for every usleep function call. And then your network connections go very strange It should be noted that Windows machines have a resolution of either 10 mS or 15 mS depending on the chipset implementation and HAL used when using the Sleep function in kernel This means that your average error will be either 5 or 7.

This is not ordinarily a problem unless you really NEED to sleep for less time than the granularity provided by Windows. Try creating a dummy loop that goes times, watch it choke your machine. If you really need usleep don't use windows. I have noticed that this consumes a lot of system CPU at least in my limited testing possibly from all of the system calls or the huge mathematical functions I used to test the effectiveness of the script.

I have only this to offer: As commented by someone else already, the gettimeofday method used below is useless - PHP will use all available CPU power doing nothing. The fsockopen method apparently is also useless - as someone else commented, an fclose was missing in the original post, but this apparently does not solve the problem.

After calling the function about 50 or so times, fsockopen returns immidiately, without any delay - and watching a process monitor in Windows, you can then watch the process taking up increasingly more memory, until eventually PHP aborts or crashes when it reaches maximum.

The win32api-method is also a no-go I have given up - I don't think there is any viable solution to this problem under PHP 4. If you need this function, upgrade your project to PHP 5. Or settle for 1-second delays with the sleep -function. These, unfortunately, seem to be your only options Dude you are SO the man for that code snippet.

It worked like a charm. I just wanted to point out a couple things and offer my own improvement. If you're like me, you were probably wondering why the socket had to keep being recreated on each call, and why you couldn't just create a static socket. Its because you hadn't enabled the right extension in php. The only real thing I did is use a static variable for the socket, to avoid creating a brand new socket on each call of this function.

I'm not sure if socket creation will cause things to crash down the line like the other problems reported on here, but if you ask me better safe then sorry.Check here to start a new keyword search. Search support or find a product: Search. Search results are not available at this time. Please try again later or use one of the other support options on this page. Watson Product Search Search. None of the above, continue with my search. This document shows how to use the C API usleep to delay a job for less than a second.

The function usleep is a C API that suspends the current process for the number of microseconds passed to it. It can be used for delaying a job. If you need to delay the job for less than a second, however, you must use the usleep API.

usleep example

It returns an integer; 0 if successful, -1 if unsuccessful. It can accept anywhere from 0 to microseconds. In these examples, the job is delayed formicroseconds, or 0. Caution: The following code snippets are examples only.

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I'm developing the game server, which is written on C. And I need to develop a cycle with a certain frequency 50 times per second to perform an algorithm. The problem is that I can't pause the program for an exact time interval - microseconds. Function usleep runs about microseconds. The result is always more on microseconds than expected.

I also tried to use function selectbut result is the same as with the sleep. It is not that your code has a problem, but the actual call to sleep, reading the time, etc. Sleeping functions on non-realtime systems are not guaranteed to sleep the exact period specified; on a busy system, the process will be woken up only when its time slice begins.

usleep(3) [php man page]

Or, as the man page puts it"system activity may lengthen the sleep by an indeterminate amount". The close-toms amount sounds like the kern. The classic workaround for this problem is the one offered by Ofir: instead of specifying a fixed sleeping interval, specify the remaining time to sleep. In average, your loop will run every 20ms, which is what you most likely want to achieve.

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Learn more. Asked 7 years, 6 months ago. Active 6 years, 1 month ago. Viewed 67k times. Explain to me, please, what's wrong with my code. Christian Ammer 6, 5 5 gold badges 40 40 silver badges 94 94 bronze badges. Andrew Andrew 1 1 gold badge 1 1 silver badge 6 6 bronze badges.

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Active Oldest Votes. Ofir Ofir 7, 1 1 gold badge 25 25 silver badges 42 42 bronze badges. To add to the answer: the sleep commands release the processor for a set time duration. During this delay, the process do not ask for the processor and is not part of the scheduler process elections.

Once the timer expires, the process will reenter in competition with the other process for the CPU use.

usleep example

The additional delay comes from the scheduler choice to elect your program or not at each election time. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. The Overflow Blog. Podcast Cryptocurrency-Based Life Forms. Q2 Community Roadmap.

Featured on Meta. Community and Moderator guidelines for escalating issues via new response….C programming language provides sleep function in order to wait for a current thread for a specified time. Of course, the CPU and other processes will run without a problem. We can include this library as below. If we are writing an application which will run on the windows platform we should include windows.

Actually there is no cross plat format default library. But we can write our application which will use the proper library according to compile architecture. In this part, we will use sleep function in an example. In this example, we want to sleep for 1 second. We can also sleep for 10 seconds without a problem.

As stated previously the sleep function will interpret given value as the second. What if we need to sleep in milliseconds which is lower than second. We can use decimal or float values. In this example, we will sleep for 10 millisecond which can be expressed like 0. We can also use usleep function which will sleep given value in a microsecond. Thanks for your correction. Thanks for the help. We have corrected it. I think it should be Sleep on windows.By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service.

The dark mode beta is finally here. Change your preferences any time. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. I'm developing the game server, which is written on C. And I need to develop a cycle with a certain frequency 50 times per second to perform an algorithm. The problem is that I can't pause the program for an exact time interval - microseconds.

Function usleep runs about microseconds. The result is always more on microseconds than expected. I also tried to use function selectbut result is the same as with the sleep. It is not that your code has a problem, but the actual call to sleep, reading the time, etc.

Sleeping functions on non-realtime systems are not guaranteed to sleep the exact period specified; on a busy system, the process will be woken up only when its time slice begins. Or, as the man page puts it"system activity may lengthen the sleep by an indeterminate amount". The close-toms amount sounds like the kern. The classic workaround for this problem is the one offered by Ofir: instead of specifying a fixed sleeping interval, specify the remaining time to sleep. In average, your loop will run every 20ms, which is what you most likely want to achieve.

Learn more. Asked 7 years, 6 months ago. Active 6 years, 1 month ago. Viewed 67k times.The sleepusleepor nsleep subroutines suspend the current process until:. The suspension time might be longer than requested time due to the scheduling of other activity by the system. Upon return, the location that is specified by the Rmtp parameter is updated to show the time that is left in the interval, or 0 if the full interval is elapsed.

The sleep and usleep subroutines are simplified forms for the nsleep subroutine. The sleep subroutine suspends the current process for whole seconds. The usleep subroutine suspends the current process in microseconds, and the nsleep subroutine suspends the current process in nanoseconds.

The nsleep subroutine is the system call that is used by the AIX operating system to suspend thread execution. The sleep and usleep subroutines serve as front end to the nsleep subroutine. The actual time interval for which the process is suspended is approximate. The time interval to suspend a process might take long time because of the other activities that are scheduled by the system, or the process suspension might take less time because of a signal that preempts the suspension.

For the nsleep subroutine, your must specify the Rqtp Requested Time Pause and Rmtp Remaining Time Pause parameters so that the actual time for which the process is suspended can be identified.

Normally, the value in Rmtp parameter is the equivalent of zero. By design, the maximum value that might be used in the Rqtp parameter is the number of nanoseconds in one second.

The nsleepsleepand usleep subroutines return a value of 0 if the requested time is elapsed. If the nsleep subroutine returns a value of -1, the notification of a signal or event was received and the Rmtp parameter is updated to the requested time minus the time slept unslept timeand the errno global variable is set.

usleep example

If the sleep subroutine returns because of a premature arousal due to delivery of a signal, the return value is the unslept amount the requested time minus the time slept in seconds.

If the nsleep subroutine fails, a value of -1 is returned and the errno global variable is set to one of the following error codes:.

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The sleep subroutine is always successful and no return value is reserved to indicate an error. Purpose Suspends a current process from execution. Library Standard C Library libc. Item Description Rqtp Time interval specified for suspension of execution. Rmtp Specifies the time is left on the interval timer or 0.

Seconds Specifies time interval in seconds. Useconds Specifies time interval in microseconds. This parameter is available only for the usleep subroutine. To suspend a current running process for 10 seconds, enter the following command: sleep Item Description EINTR A signal was detected by the calling process and control is returned from the signal-catching routine, or the process is notified of an event through an event notification function. Specifies time interval in microseconds.

A signal was detected by the calling process and control is returned from the signal-catching routine, or the process is notified of an event through an event notification function.

What Is sleep() function and How To Use It In C Program?

The Rqtp parameter specified a nanosecond value less than zero or greater than or equal to 1 second. An argument address referenced informed memory.The QThread class provides a platform-independent way to manage threads.

A QThread object manages one thread of control within the program. QThreads begin executing in run. By default, run starts the event loop by calling exec and runs a Qt event loop inside the thread. You can use worker objects by moving them to the thread using QObject::moveToThread. The code inside the Worker's slot would then execute in a separate thread.

However, you are free to connect the Worker's slots to any signal, from any object, in any thread. It is safe to connect signals and slots across different threads, thanks to a mechanism called queued connections. Another way to make code run in a separate thread, is to subclass QThread and reimplement run. For example:. In that example, the thread will exit after the run function has returned.

There will not be any event loop running in the thread unless you call exec.

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It is important to remember that a QThread instance lives in the old thread that instantiated it, not in the new thread that calls run. This means that all of QThread's queued slots and invoked methods will execute in the old thread. Thus, a developer who wishes to invoke slots in the new thread must use the worker-object approach; new slots should not be implemented directly into a subclassed QThread.

Unlike queued slots or invoked methods, methods called directly on the QThread object will execute in the thread that calls the method. When subclassing QThread, keep in mind that the constructor executes in the old thread while run executes in the new thread. If a member variable is accessed from both functions, then the variable is accessed from two different threads.

Check that it is safe to do so. Note: Care must be taken when interacting with objects across different threads. See Synchronizing Threads for details.


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