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Wait/Pause function in C?

Posted on 1998-06-16
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Last Modified: 2010-04-15
Is there a function in C that will pause for a specified amount of time?
If so, what library must I #include?

Thanks
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Question by:GreatOne
15 Comments
 
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Expert Comment

by:ozo
ID: 1251240
#include <unistd.h>

unsigned int sleep(unsigned int seconds);

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Accepted Solution

by:
sganta earned 20 total points
ID: 1251241
Hi !

You use

sleep(20);  /* It sleeps for 20 seconds */;


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Expert Comment

by:Norbert
ID: 1251242
He did not say which system he uses the VC online help says:
standard dos compiler do not have the sleep function
remember msc 5.1 or 6.0 ?
Sleep
Windows NT Yes
Win95           Yes
Win32s         Yes

Import Library kernel32.lib

Header File winbase.h

Unicode No

Platform Notes None
this function works always:
void wait(time_t TimeToWait)
{
      time_t StartTime=time(NULL);
      time_t ActualTime;
      do
      {  
            ActualTime=time(NULL);
            if((StatTime+TimeToWait)>=ActualTime)
                    break;
             if(ActualTime<StartTime) //Midnight crossing
                 StartTime=ActualTime;//this is not a good solution but it prevents the loop running endless
      }while(TRUE)
}
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Expert Comment

by:Norbert
ID: 1251243
I forgot
#include <time.h>
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Author Comment

by:GreatOne
ID: 1251244
I am using a DOS compiler. Norbert, I tried using your wait function but it won't compile. I get a message that it doesn't know what TRUE is. Also, how would i call wait? do i just call it as wait(number of secs I want to wait) or another way?


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Expert Comment

by:Norbert
ID: 1251245
Ok If True is not defined make while(1)
the resolution of the time function is second
therefore you will call for a 2 sec wait
wait(2)

If you like my answer and it works for you please reopen the question  

if you need a higher resolution than seconds here a trick:
WaitHighRes(unsigned long TimeToWait)
{
volatile long *Biostime=(long*)0x0000046c; //adress of bios timer  using dos
unsigned long Starttime=*Biostime;
unsigned long  time_t ActualTime;
      do
      {   
            ActualTime=*Biostime;
            if((StatTime+TimeToWait)>=ActualTime)
                    break;
             if(ActualTime<StartTime) //Midnight crossing
                 StartTime=ActualTime;//this is not a good solution but it prevents the loop running endless
      }while(1)
}
now you have a resolution of 1/18.2 s
that means you can call
WaitHighRes(18) for waiting 1 second
Hope that helps
Norbert
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Expert Comment

by:Norbert
ID: 1251246
for security reasons to not depend on model small, medium compact, large or huge change the line
volatile long *Biostime=(long*)0x0000046c; //adress of bios timer  using dos
to
volatile long far*Biostime=(long far*)0x0000046c; //adress of bios timer  using dos
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Author Comment

by:GreatOne
ID: 1251247
Norton,
I made the changes and now it compiles but it does not pause at all. I will try your other function and see if that works. if it does, i will reopen the question for you.
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Expert Comment

by:Norbert
ID: 1251248
why does it not pause ?
please send the code you have written
it *must* wait
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Expert Comment

by:Norbert
ID: 1251249
GreatOne does it work ? Nothing heared from you
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Author Comment

by:GreatOne
ID: 1251250
Norbert,
Sorry for no response. Here is the code i used:

#include <stdio.h>
#include <stdlib.h>
#include <time.h>    


void wait(time_t TimeToWait)
{

time_t StartTime=time(NULL);
time_t ActualTime;
do
{
ActualTime=time(NULL);
if((StartTime+TimeToWait)>=ActualTime)break;
if(ActualTime<StartTime) //Midnight crossing
StartTime=ActualTime;//this is not a good solution but it prevents the loop running endless
}while(1);
}


void main()
{
      printf("testing wait function..");
      wait(10);
      printf("wait function called.\n");
}

like i said, there is no pause. any ideas?
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Expert Comment

by:Norbert
ID: 1251251
In my Original Post I made a stupid typo:
The Line
          if((StartTime+TimeToWait)>=ActualTime)break;
is wrong it must be
          if((StartTime+TimeToWait)<=ActualTime)break;
I have tested it and it works for me

BTW
I don't know wich time period but answers are auto grade as I know if there is a long time no activity
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Expert Comment

by:Norbert
ID: 1251252
Wait function no more needed ??

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Author Comment

by:GreatOne
ID: 1251253
Thanks Norbert. Everything works perfectly now. Sorry about the long delay.
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Expert Comment

by:Norbert
ID: 1251254
Fine that it works but did you recognize that an other gets the points?

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