implement time delay in c

Question

I don t know exactly how to word a search for this   so I haven t had any luck finding anything    S  I need to implement a time delay in C   for example I want to do some stuff  then wait say 1 minute  then continue on doing stuff   Did that make sense  Can anyone help me out

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Try sleep int number of seconds

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For delays as large as one minute  sleep   is a nice choice   If someday  you want to pause on delays smaller than one second  you may want to consider poll   with a timeout   Both are POSIX

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C11 has a function specifically for this    include  lt threads h gt   include  lt time h gt   include  lt stdio h gt   void sleep time t seconds        struct timespec time      time tv sec   seconds      time tv nsec   0      while  thrd sleep  amp time   amp time         int main         puts  Sleeping for 5 seconds           sleep 5       puts  Done         return 0      Note that this is only available starting in glibc 2 28

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Is it timer    For WIN32 try http   msdn microsoft com en-us library ms687012 28VS 85 29 aspx

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you can simply call delay   function  So if you want to delay the process in 3 seconds  call delay 3000

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sleep int  works as a good delay  For a minute     Doing some stuff    sleep 60     Freeze for A minute   Continue doing stuff

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Here is how you can do it on most desktop systems    ifdef  WIN32      include  lt windows h gt   else      include  lt unistd h gt   endif  void wait  int seconds          Pretty crossplatform  both ALL POSIX compliant systems AND Windows      ifdef  WIN32         Sleep  1000   seconds         else         sleep  seconds         endif    int main  int argc  char   argv        int running   3      while  running              do something         --running          wait  3              return 0     OK     Here is how you can do it on a microcomputer   processor w o timer   int wait loop0   10000  int wait loop1   6000      for microprocessor without timer  if it has a timer refer to vendor documentation and use it instead  void wait  int seconds          this function needs to be finetuned for the specific microprocessor     int i  j  k      for i   0  i  lt  seconds  i                  for j   0  j  lt  wait loop0  j                          for k   0  k  lt  wait loop1  k                       waste function  volatile makes sure it is not being optimized out by compiler                 int volatile t   120   j   i   k                  t   t   5                                   int main  int argc  char   argv        int running   3      while  running              do something         --running          wait  3              return 0     OK     The waitloop variables must be fine tuned  those did work pretty close for my computer  but the frequency scale thing makes it very imprecise for a modern desktop system  So don t use there unless you re bare to the metal and not doing such stuff

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for C use in gcc   include  lt windows h gt  then use Sleep        Sleep   with capital S  not sleep   with s     Sleep 1000  is 1 sec     maybe  clang supports sleep    sleep 1  is for 1 sec time delay wait

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For short delays  say  some microseconds  on Linux OS  you can use  quot usleep quot      C Program to perform short delays  include  lt unistd h gt   include  lt stdio h gt   int main        printf  quot Hello  n quot        usleep 1000000      For a 1-second delay     printf  quot Bye  n       return 0

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Although many implementations have the time function return the current time in seconds  there is no guarantee that every implementation will do so  e g  some may return milliseconds rather than seconds   As such  a more portable solution is to use the difftime function   difftime is guaranteed by the C standard to return the difference in time in seconds between two time t values  As such we can write a portable time delay function which will run on all compliant implementations of the C standard    include  lt time h gt   void delay double dly          save start time        const time t start   time NULL        time t current      do             get current time            time  amp current               break loop when the requested number of seconds have elapsed         while difftime current  start   lt  dly         One caveat with the time and difftime functions is that the C standard never specifies a granularity  Most implementations have a granularity of one second  While this is all right for delays lasting several seconds  our delay function may wait too long for delays lasting under one second   There is a portable standard C alternative  the clock function      The clock function returns the implementation   s best approximation to the processor time used by the program since the beginning of an implementation-defined era related only to the program invocation  To determine the time in seconds  the value returned by the clock function should be divided by the value of the macro CLOCKS PER SEC    The clock function solution is quite similar to our time function solution    include  lt time h gt   void delay double dly          save start clock tick        const clock t start   clock         clock t current      do             get current clock tick            current   clock                break loop when the requested number of seconds have elapsed         while  double  current-start  CLOCKS PER SEC  lt  dly       There is a caveat in this case similar to that of time and difftime  the granularity of the clock function is left to the implementation  For example  machines with 32-bit values for clock t with a resolution in microseconds may end up wrapping the value returned by clock after 2147 seconds  about 36 minutes    As such  consider using the time and difftime implementation of the delay function for delays lasting at least one second  and the clock implementation for delays lasting under one second   A final word of caution  clock returns processor time rather than calendar time  clock may not correspond with the actual elapsed time  e g  if the process sleeps

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Write this code    void delay int x      int i 0 j 0      for i 0 i lt x i    for j 0 j lt 200000 j          int main         int i num       while 1         delay 500        printf  Host name        printf   n

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system  timeout  t 60       waits 60s  this is only for windows vista 7 8 system  ping -n 60 127 0 0 1  gt nul       waits 60s  for all windows

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What operating system are you using  I know that on windows  you can do something like this    include crap  include  lt windows h gt   int main          do things   Sleep    ur wait time in ms        wait for param1 ms     continue to do things

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Provides ANSI C method of delaying x milliseconds   include  lt stdio h gt   include  lt stdlib h gt   include  lt time h gt   void delayMillis unsigned long ms        clock t start ticks   clock        unsigned long millis ticks   CLOCKS PER SEC 1000      while  clock  -start ticks  lt  ms millis ticks                        Example output         CLOCKS PER SEC  1000000         Test Delay of 800 ms            start 2054   end 802058       elapsedSec  0 802058      int testDelayMillis          printf  CLOCKS PER SEC   lu  n n   CLOCKS PER SEC       clock t start t  end t      start t   clock        printf  Test Delay of 800 ms     n   CLOCKS PER SEC       delayMillis 800        end t   clock        double elapsedSec   end t  double CLOCKS PER SEC      printf   nstart  lu   end  lu    nelapsedSec   f  n   start t  end t  elapsedSec       int main             testDelayMillis

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If you are certain you want to wait and never get interrupted then use sleep in POSIX or Sleep in Windows  In POSIX sleep takes time in seconds so if you want the time to be shorter there are varieties like usleep   which uses microseconds  Sleep in Windows takes milliseconds  it is rare you need finer granularity than that   It may be that you wish to wait a period of time but want to allow interrupts  maybe in the case of an emergency  sleep can be interrupted by signals but there is a better way of doing it in this case   Therefore I actually found in practice what you do is wait for an event or a condition variable with a timeout   In Windows your call is WaitForSingleObject  In POSIX it is pthread cond timedwait   In Windows you can also use WaitForSingleObjectEx and then you can actually  interrupt  your thread with any queued task by calling QueueUserAPC  WaitForSingleObject Ex  will return a code determining why it exited  so you will know when it returns a  TIMEDOUT  status that it did indeed timeout  You set the Event it is waiting for when you want it to terminate   With pthread cond timedwait you can signal broadcast the condition variable   If several threads are waiting on the same one  you will need to broadcast to wake them all up   Each time it loops it should check the condition  Your thread can get the current time and see if it has passed or it can look to see if some condition has been met to determine what to do  If you have some kind of queue you can check it   Your thread will automatically have a mutex locked that it used to wait on the condition variable  so when it checks the condition it has sole access to it

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In standard C  C99   you can use time   to do this  something like    include  lt time h gt    void waitFor  unsigned int secs        unsigned int retTime   time 0    secs       Get finishing time      while  time 0   lt  retTime                    Loop until it arrives      By the way  this assumes time   returns a 1-second resolution value  I don t think that s mandated by the standard so you may have to adjust for it     In order to clarify  this is the only way I m aware of to do this with ISO C99  and the question is tagged with nothing more than  C  which usually means portable solutions are desirable although  of course  vendor-specific solutions may still be given    By all means  if you re on a platform that provides a more efficient way  use it  As several comments have indicated  there may be specific problems with a tight loop like this  with regard to CPU usage and battery life   Any decent time-slicing OS would be able to drop the dynamic priority of a task that continuously uses its full time slice but the battery power may be more problematic   However C specifies nothing about the OS details in a hosted environment  and this answer is for ISO C and ISO C alone  so no use of sleep  select  Win32 API calls or anything like that    And keep in mind that POSIX sleep can be interrupted by signals  If you are going to go down that path  you need to do something like   int finishing   0     set finishing in signal handler                        if you want to really stop   void sleepWrapper  unsigned int secs        unsigned int left   secs      while   left  gt  0   amp  amp    finishing      Don t continue if signal has         left   sleep  left                  indicated exit needed

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There are no sleep   functions in the pre-C11 C Standard Library  but POSIX does provide a few options   The POSIX function sleep    unistd h  takes an unsigned int argument for the number of seconds desired to sleep  Although this is not a Standard Library function  it is widely available  and glibc appears to support it  even when compiling with stricter settings like --std c11   The POSIX function nanosleep    time h  takes two pointers to timespec structures as arguments  and provides finer control over the sleep duration  The first argument specifies the delay duration  If the second argument is not a null pointer  it holds the time remaining if the call is interrupted by a signal handler   Programs that use the nanosleep   function may need to include a feature test macro in order to compile  The following code sample will not compile on my linux system without a feature test macro when I use a typical compiler invocation of gcc -std c11 -Wall -Wextra -Wpedantic   POSIX once had a usleep   function  unistd h  that took a useconds t argument to specify sleep duration in microseconds  This function also required a feature test macro when used with strict compiler settings  Alas  usleep   was made obsolete with POSIX 1-2001 and should no longer be used  It is recommended that nanosleep   be used now instead of usleep      define  POSIX C SOURCE  199309L        feature test macro for nanosleep     include  lt stdio h gt   include  lt unistd h gt        for sleep    include  lt time h gt          for nanosleep    int main void           use unsigned sleep unsigned seconds      puts  Wait 5 sec           sleep 5           use int nanosleep const struct timespec  req  struct timespec  rem       puts  Wait 2 5 sec           struct timespec ts      tv sec   2              seconds to wait                             tv nsec   5e8           additional nanoseconds     nanosleep  amp ts  NULL       puts  Bye         return 0      Addendum   C11 does have the header threads h providing thrd sleep    which works identically to nanosleep    GCC did not support threads h until 2018  with the release of glibc 2 28  It has been difficult in general to find implementations with support for threads h  Clang did not support it for a long time  but I m not sure about the current state of affairs there   You will have to use this option with care

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Check sleep 3  man page or MSDN for Sleep

[c] implement time delay in c

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