sleep

问题 As a possible alternative to using cron jobs, I found the sleep function. I have never used this before. If I tell my script to run inside a kind of loop, and inside that loop I have an instruction like this # sleeps for 86400 seconds or one day sleep(86400); will my script be launched again after 1 day? even if don't access it on my web browser again within that period? I think is not possible, but I'm here to ask an expert about it. 回答1: The main problem with using PHP this way is, in my

问题 I have an app which is one activity. Everything works as I would expect except when I put the phone (a Samsung Galaxy Ace running Gingerbread) to sleep with the button on the side. When I do this, the following are called (in this order): onPause, onStop, onDestroy, onCreate, onStart, onResume, onPause . This is without waking the phone up , it is still asleep - screen is off. Why is the activity killed completely and re-recreated? Even more bizarre, if the phone is then switched back on the

问题 Note the capital "S" in Sleep . Sleep with a capital "S" is a standard function that sleeps milliseconds on the PC. On Mac OS X, there is no such symbol. However, the Xcode linking environment seems to find something to link it to. What is it? 回答1: Well, it’s an old old Carbon function (in the CoreServices / OSServices framework) that puts the computer to sleep. I can’t find any documentation. Sleep and Xcode 回答2: sleep(int) is a method from the unix system that run mac Known as Darwin. Here

问题 Doing some maintenance on a script, I found this line: ping -n 40 127.0.0.1 > NUL 2>&1 I know from this question that everything up to the NUL causes the script to sleep for 39 seconds. But I don't know what the rest of the command does. What does the 2>&1 do? 回答1: Decomposing the line ping -n 40 127.0.0.1 Send 40 ping packets to local host. If there is not any problem the default behaviour is to wait 1 second between packets, so it generates a 39 second delay >nul or 1>nul Redirects anything

问题 Our code is written in C++ 11 (VS2012/Win 7-64bit). The C++ library provides a sleep_for function that we use. We observed that the C++ sleep_for sometimes shows a large overshoot. In other words we request to sleep for say 15 ms but the sleep turns out to be e.g. 100 ms. We see this when the load on the system is high. My first reaction: “of course the sleeps "take longer" if there is a lot of load on the system and other threads are using the CPU”. However the “funny” thing is that if we

问题 I want to use clock_nanosleep for waiting of 1 microsec.. As far as I understand, I have to give an absolute time as input. Is the following code okay in this case? deadline.tv_sec = 0; deadline.tv_nsec = 1000; clock_nanosleep(CLOCK_REALTIME, TIMER_ABSTIME, &deadline, NULL); 回答1: As far as I understand, I have to give an absolute time as input. No, the flags argument allows you to choose relative or absolute time. You want clock_nanosleep(CLOCK_REALTIME, 0, &deadline, NULL); to specify one

问题 Is there a way to disable the screen saver and the display sleep with cocoa? 回答1: The use of UpdateSystemActivity(OverallAct) has been deprecated in OSX 10.8. The recommended approach is now to block it with the following call: IOPMAssertionCreateWithName(kIOPMAssertionTypePreventUserIdleDisplaySleep, kIOPMAssertionLevelOn, reasonForActivity, &assertionID); See this Apple Q&A for further details. 回答2: i've just solved it and forgot to post it as an answer. Calling UpdateSystemActivity

问题 When including the sleep function from unistd.h the program hangs indefinitely: #include <stdio.h> #include <unistd.h> int main() { int i; printf("0 "); for(i = 1; i <20; ++i) { sleep(2); printf("%d ", i); } printf("\n"); return 0; } The rest runs fine when sleep(2) is commented out, any ideas? 回答1: There's nothing wrong with the code, but note that in many cases the output of printf is buffered, meaning that the output appears on the console only if you explicitly call fflush(stdout) , you

问题 When including the sleep function from unistd.h the program hangs indefinitely: #include <stdio.h> #include <unistd.h> int main() { int i; printf("0 "); for(i = 1; i <20; ++i) { sleep(2); printf("%d ", i); } printf("\n"); return 0; } The rest runs fine when sleep(2) is commented out, any ideas? 回答1: There's nothing wrong with the code, but note that in many cases the output of printf is buffered, meaning that the output appears on the console only if you explicitly call fflush(stdout) , you

问题 I have a number of threads (100's) that each execute for a few seconds at a time. When they are executing, they spend a significant amount of that time waiting for a response from another system (a serial device). I am mindful that having 100 threads executing at once could be a resource hog so I actually limit the number of threads that can start at any one time. It occurs to me though that there must be good and bad ways of waiting for an external event inside a thread. Is this approach CPU