How to use timer in C

Question

What is the method to use a timer in C  I need to wait until 500 ms for a job  Please mention any good way to do this job  I used sleep 3   But this method does not do any work in that time duration  I have something that will try until that time to get any input

User · Accepted Answer

You can use a time t struct and clock   function from time h   Store the start time in a time t struct by using clock   and check the elapsed time by comparing the difference between stored time and current time

User · Answer

May be this examples help to you   include  lt stdio h gt   include  lt time h gt   include  lt stdlib h gt           Implementation simple timeout      Input  count milliseconds as number      Usage          setTimeout 1000  - timeout on 1 second         setTimeout 10100  - timeout on 10 seconds and 100 milliseconds     void setTimeout int milliseconds           If milliseconds is less or equal to 0        will be simple return from function without throw error     if  milliseconds  lt   0            fprintf stderr   Count milliseconds for timeout is less or equal to 0 n            return                a current time of milliseconds     int milliseconds since   clock     1000   CLOCKS PER SEC          needed count milliseconds of return from this timeout     int end   milliseconds since   milliseconds          wait while until needed time comes     do           milliseconds since   clock     1000   CLOCKS PER SEC        while  milliseconds since  lt   end       int main             input from user for time of delay in seconds     int delay      printf  Enter delay          scanf   d    amp delay           counter downtime for run a rocket while the delay with more 0     do              erase the previous line and display remain of the delay         printf   033 ATime left for run rocket   d n   delay               a timeout for display         setTimeout 1000               decrease the delay to 1         delay--         while  delay  gt   0           a string for display rocket     char rocket 3     -- gt            a string for display all trace of the rocket and the rocket itself     char  rocket trace    char    malloc 100   sizeof char            display trace of the rocket from a start to the end     int i      char passed way 100            for  i   0  i  lt   50  i              setTimeout 25           sprintf rocket trace    s s   passed way  rocket           passed way i                 printf   033 A            printf     s n   rocket trace                 erase a line and write a new line     printf   033 A        printf   033 2K        puts  Good luck          return 0      Compile file  run and delete after  my preference     gcc timeout c -o timeout  amp  amp    timeout  amp  amp  rm timeout   Try run it for yourself to see result   Notes   Testing environment    uname -a Linux wlysenko-Aspire 3 13 0-37-generic  64-Ubuntu SMP Mon Sep 22 21 28 38 UTC 2014 x86 64 x86 64 x86 64 GNU Linux   gcc --version gcc  Ubuntu 4 8 5-2ubuntu1 14 04 1  4 8 5 Copyright  C  2015 Free Software Foundation  Inc  This is free software  see the source for copying conditions   There is NO warranty  not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE

User · Answer

Yes  you need a loop   If you already have a main loop  most GUI event-driven stuff does  you can probably stick your timer into that   Use    include  lt time h gt   time t my t  fire t    Then  for times over 1 second   initialize your timer by reading the current time    my t   time NULL     Add the number of seconds your timer should wait and store it in fire t   A time t is essentially a uint32 t  you may need to cast it   Inside your loop do another  my t   time NULL     if  my t   fire t  then consider the timer fired and do the stuff you want there   That will probably include resetting it by doing another fire t   time NULL    seconds to wait for next time   A time t is a somewhat antiquated unix method of storing time as the number of seconds since midnight 1 1 1970 but it has many advantages   For times less than 1 second you need to use gettimeofday    microseconds  or clock gettime    nanoseconds  and deal with a struct timeval or struct timespec which is a time t and the microseconds or nanoseconds since that 1 second mark   Making a timer works the same way except when you add your time to wait you need to remember to manually do the carry  into the time t  if the resulting microseconds or nanoseconds value goes over 1 second  Yes  it s messy   See man 2 time  man gettimeofday  man clock gettime   sleep    usleep    nanosleep   have a hidden benefit   You see it as pausing your program  but what they really do is release the CPU for that amount of time   Repeatedly polling by reading the time and comparing to the done time  are we there yet   will burn a lot of CPU cycles which may slow down other programs running on the same machine  and use more electricity battery    It s better to sleep   most of the time then start checking the time   If you re trying to sleep and do work at the same time you need threads

User · Answer

Here s a solution I used  it needs  include  lt time h gt      int msec   0  trigger   10     10ms    clock t before   clock     do             Do something to busy the CPU just here while you drink a coffee      Be sure this code will not take more than  trigger  ms          clock t difference   clock   - before    msec   difference   1000   CLOCKS PER SEC    iterations      while   msec  lt  trigger     printf  Time taken  d seconds  d milliseconds   d iterations  n     msec 1000  msec 1000  iterations

[c] How to use timer in C?

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