how to stop a process?

frostmagic · 11-30-2003, 09:24 AM

how to i stop a program for a certain amount of time like in millisecs and micro secs? i try using sleep but it must be in integer.

MartinN · 11-30-2003, 09:32 AM

If you are talking C, try usleep(microseconds)

Regards
Martin

frostmagic · 12-02-2003, 09:18 AM

i have done the usleep but then it dont really work well
how do i test whether the correct timing was done?
like supposed
sending A was to be done in 10us and B 500us and C 50us
how do i check whether the correct timing was done

MartinN · 12-02-2003, 10:54 AM

I have no idea. I don't think you can expect that kind of precision out of an operating system that doesn't claim to be an RTOS (Real Time OS).

Take a look at this little test:

Code:

#include <sys/timeb.h>
#include <unistd.h>

int main ()
{
  struct timeb time1;
  struct timeb time2;
  unsigned int millisecdiff;
  ftime(&time1);

  /*sleep 1 millisecond*/
  usleep(1000);

  ftime(&time2);

  millisecdiff= time2.millitm - time1.millitm + 1000 * (time2.time - time1.time);  
  printf ("Milliseconds elapsed: %d\n", millisecdiff);
}

You could expect that this should return 1 every time and possibly 2 a few times. It doesn't! It varies between 2 and as much as 14 on my machine.

May I ask what on earth you need that kind of precision for?

Regards
Martin

h/w · 12-03-2003, 12:09 PM

can u give a sleep(0.001) for a 1ms delay?

then theres always usleep(xxx).

frostmagic · 12-04-2003, 12:01 PM

sleep in linux must be an integer

h/w · 12-04-2003, 01:36 PM

yes i know, but put sleep (0.001), and see - it WILL compile with no warnings even, and give (im assuming its a msec cos it is definitely less time than a sleep(1)) a delay of a msec.

(yes, im on linux too)

Hko · 12-04-2003, 03:10 PM

The compiler doesn't give any error or even warnings when passing "0.01", not even with all warnings turned on (gcc -Wall -pedantic -ansi ...). But this is not only for sleep(). I've no idea why.

Probably sleep() has a minimal sleeping time, like nanosleep() has (10 or 1 ms depending on platform).

Anyways, it's not the right way to have a program sleep for a while. Use usleep(), or better yet, nanosleep() or select().

h/w · 12-04-2003, 03:16 PM

u think it could be to do with gcc3.x?

Hko · 12-04-2003, 04:52 PM

I just tried with gcc-2.95.
Same thing: no warnings.

infamous41md · 12-04-2003, 07:10 PM

this program:

Code:

#include <unistd.h>

int main(int argc, char **argv)
{
        if(argc == 1) sleep(.1);
        else if(argc == 2) sleep(1);
}

does this:

Code:

<:n00b@highjack3d:> ltrace ./a.out 1
__libc_start_main(0x08048328, 2, 0xbffffa94, 0x08048230, 0x08048388 <unfinished ...>
sleep(1)                                          = 0
+++ exited (status 0) +++
<:n00b@highjack3d:> ltrace ./a.out 
__libc_start_main(0x08048328, 1, 0xbffffa94, 0x08048230, 0x08048388 <unfinished ...>
sleep(0)                                          = 0
+++ exited (status 0) +++

anything less than 0 is interpreted as 0.

h/w · 12-04-2003, 07:33 PM

ahh great. thanks man.
may i ask what u used to debug there?

h/w · 12-04-2003, 07:39 PM

sorry for askin - didnt realize ltrace was a tool out there. was thinking it was something inside some debugger like gdb.

infamous41md · 12-05-2003, 10:58 AM

yea ltrace is a great tool, as is 'strace' if you hadn't known of that already.

h/w · 12-05-2003, 11:02 AM

yeah, strace and objdump, i have tried, and they produce similar looking outputs to what you posted. which is why i was wondering what ltrace was.