How do you add a timed delay to a C program

Question

I am trying to add a timed delay in a C   program  and was wondering if anyone has any suggestions on what I can try or information I can look at   I wish I had more details on how I am implementing this timed delay  but until I have more information on how to add a timed delay I am not sure on how I should even attempt to implement this

User · Answer

Yes  sleep is probably the function of choice here  Note that the time passed into the function is the smallest amount of time the calling thread will be inactive  So for example if you call sleep with 5 seconds  you re guaranteed your thread will be sleeping for at least 5 seconds  Could be 6  or 8 or 50  depending on what the OS is doing   During optimal OS execution  this will be very close to 5    Another useful feature of the sleep function is to pass in 0  This will force a context switch from your thread   Some additional information  http   www opengroup org onlinepubs 000095399 functions sleep html

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You can also use select 2  if you want microsecond precision  this works on platform that don t have usleep 3    The following code will wait for 1 5 second    include  lt sys select h gt   include  lt sys time h gt   include  lt unistd h gt    int main         struct timeval t      t tv sec   1      t tv usec   500000      select 0  NULL  NULL  NULL   amp t

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include  lt unistd h gt  usleep 3000000     This will also sleep for three seconds  You can refine the numbers a little more though

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The top answer here seems to be an OS dependent answer  for a more portable solution you can write up a quick sleep function using the ctime header file  although this may be a poor implementation on my part     include  lt iostream gt   include  lt ctime gt   using namespace std   void sleep float seconds       clock t startClock   clock        float secondsAhead   seconds   CLOCKS PER SEC         do nothing until the elapsed time has passed      while clock    lt  startClock secondsAhead       return    int main         cout  lt  lt   Next string coming up in one second    lt  lt  endl      sleep 1 0       cout  lt  lt   Hey  what did I miss    lt  lt  endl       return 0

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On Windows you can include the windows library and use  Sleep 0    to sleep the program  It takes a value that represents milliseconds

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You can try this code snippet    include lt chrono gt   include lt thread gt   int main        std  this thread  sleep for std  chrono  nanoseconds 10        std  this thread  sleep until std  chrono  system clock  now     std  chrono  seconds 1

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An updated answer for C  11   Use the sleep for and sleep until functions    include  lt chrono gt   include  lt thread gt   int main         using namespace std  this thread     sleep for  sleep until     using namespace std  chrono     nanoseconds  system clock  seconds      sleep for nanoseconds 10        sleep until system clock  now     seconds 1        With these functions there s no longer a need to continually add new functions for better resolution  sleep  usleep  nanosleep  etc  sleep for and sleep until are template functions that can accept values of any resolution via chrono types  hours  seconds  femtoseconds  etc   In C  14 you can further simplify the code with the literal suffixes for nanoseconds and seconds    include  lt chrono gt   include  lt thread gt   int main         using namespace std  this thread         sleep for  sleep until     using namespace std  chrono literals     ns  us  ms  s  h  etc      using std  chrono  system clock       sleep for 10ns       sleep until system clock  now     1s       Note that the actual duration of a sleep depends on the implementation  You can ask to sleep for 10 nanoseconds  but an implementation might end up sleeping for a millisecond instead  if that s the shortest it can do

User · Answer

In Win32   include lt windows h gt  Sleep milliseconds    In Unix   include lt unistd h gt  unsigned int microsecond   1000000  usleep 3   microsecond    sleeps for 3 second  sleep   only takes a number of seconds which is often too long

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Do you want something as simple like   include  lt unistd h gt  sleep 3    sleeps for 3 second

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Note that this does not guarantee that the amount of time the thread sleeps will be anywhere close to the sleep period  it only guarantees that the amount of time before the thread continues execution will be at least the desired amount  The actual delay will vary depending on circumstances  especially load on the machine in question  and may be orders of magnitude higher than the desired sleep time   Also  you don t list why you need to sleep but you should generally avoid using delays as a method of synchronization

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Many others have provided good info for sleeping   I agree with Wedge that a sleep seldom the most appropriate solution   If you are sleeping as you wait for something  then you are better off actually waiting for that thing event   Look at Condition Variables for this     I don t know what OS you are trying to do this on  but for threading and synchronisation you could look to the Boost Threading libraries  Boost Condition Varriable    Moving now to the other extreme if you are trying to wait for exceptionally short periods then there are a couple of hack style options   If you are working on some sort of embedded platform where a  sleep  is not implemented then you can try a simple loop  for while etc  with an empty body  be careful the compiler does not optimise it away    Of course the wait time is dependant on the specific hardware in this case  For really short  waits  you can try an assembly  nop    I highly doubt these are what you are after but without knowing why you need to wait it s hard to be more specific

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Syntax   void sleep unsigned seconds    sleep   suspends execution for an interval  seconds   With a call to sleep  the current program is suspended from execution for the number of seconds specified by the argument seconds  The interval is accurate only to the nearest hundredth of a second or to the accuracy of the operating system clock  whichever is less accurate

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I found that   sleep milliseconds     without the quotes  works well for Win32 if you include the chrono library  E g    include  lt chrono gt   using namespace std   main       cout  lt  lt   text   lt  lt  endl       sleep 10000      pauses for 10 seconds     Make sure you include the underscore before sleep

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to delay output in cpp for fixed time  you can use the Sleep   function by including windows h header file syntax for Sleep   function is Sleep time in ms  as  cout lt  lt  Apple n   Sleep 3000   cout lt  lt  Mango     OUTPUT  above code will print Apple and wait for 3 seconds before printing Mango

[c++] How do you add a timed delay to a C++ program?

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