Faster than Crontab

majorlinux · 03-26-2009, 06:49 PM

Is there anything faster than crontab? I am working on a project and need crontab to run faster than it currently does. Is that possible or is there software I can install to get it to do that?

watcher69b · 03-26-2009, 07:44 PM

what do you mean 'faster'?

majorlinux · 03-27-2009, 09:28 AM

I need something that will run more often than a minute.

chrism01 · 03-28-2009, 01:20 AM

My rule of thumb is that its a waste of resources to ask cron to keep initialising new processes more than every 5 mins. There's quite an overhead, it has to create a whole new proc env every time.
Use a daemon containing infinite loop and wait as long or short as reqd at the bottom of the loop.

majorlinux · 03-28-2009, 02:13 AM

Quote:

Originally Posted by chrism01

My rule of thumb is that its a waste of resources to ask cron to keep initialising new processes more than every 5 mins. There's quite an overhead, it has to create a whole new proc env every time.
Use a daemon containing infinite loop and wait as long or short as reqd at the bottom of the loop.

Can you give me an example of that?

jlinkels · 03-28-2009, 07:54 AM

Code:

#!/bin/bash
while [ 1 ]
   do
   /path/to/your/program
   sleep 20
done

jlinkels

majorlinux · 03-28-2009, 09:17 AM

Quote:

Originally Posted by jlinkels

Code:

#!/bin/bash
while [ 1 ]
   do
   /path/to/your/program
   sleep 20
done

jlinkels

So does that sleep it from 20 seconds or 20 minutes? I'm assuming seconds.

tredegar · 03-28-2009, 12:13 PM

From man sleep:

Code:

SYNOPSIS
       sleep NUMBER[SUFFIX]...
       sleep OPTION

DESCRIPTION
       Pause  for  NUMBER  seconds.  SUFFIX may be ‘s’ for seconds (the default), ‘m’ for minutes, ‘h’ for hours or ‘d’ for
       days.  Unlike most implementations that require NUMBER be an integer, here NUMBER may be an arbitrary floating point
       number.  Given two or more arguments, pause for the amount of time specified by the sum of their values.

majorlinux · 03-28-2009, 12:20 PM

Quote:

Originally Posted by tredegar

From man sleep:

Code:

SYNOPSIS
       sleep NUMBER[SUFFIX]...
       sleep OPTION

DESCRIPTION
       Pause  for  NUMBER  seconds.  SUFFIX may be ‘s’ for seconds (the default), ‘m’ for minutes, ‘h’ for hours or ‘d’ for
       days.  Unlike most implementations that require NUMBER be an integer, here NUMBER may be an arbitrary floating point
       number.  Given two or more arguments, pause for the amount of time specified by the sum of their values.

Cool...cool...Thanks

jlinkels · 03-28-2009, 12:46 PM

Quote:

Originally Posted by majorlinux

So does that sleep it from 20 seconds or 20 minutes?

20 hours.

If you are too lazy to read the manual page or to check the TLDP website I am sorry to have put in my time to help you.

jlinkels

majorlinux · 03-28-2009, 12:48 PM

Quote:

Originally Posted by jlinkels

20 hours.

If you are too lazy to read the manual page or to check the TLDP website I am sorry to have put in my time to help you.

jlinkels

I mean, I only asked because I'm not at the server right now. So many angry people...

tredegar · 03-28-2009, 01:04 PM

Please calm down.
It's worth remembering that the interweb knows almost everything there is to know about, including man pages. Eg here:
http://linux.die.net/man/
They come nicely formatted too

robel · 03-28-2009, 01:32 PM

Quote:

Originally Posted by jlinkels

Code:

#!/bin/bash
while [ 1 ]
   do
   /path/to/your/program
   sleep 20
done

Nice, but what if you want this, like the subject says, to be like cron? I mean, what if you want the program to be run at 00:00:00, then at 00:00:20, then at 00:00:40, then at 00:01:00, then at 00:01:20, and so on.

Now, add the fact that 'program' runs between 1 and 10 seconds so a simple 'sleep' would not do the trick. You would like a 'sleep 20 sec measured from the previous sleep including running time of the program'.

'program' can look like this:

Code:

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

int main (void)
{
    srandom(time(NULL));
    sleep((int)(10*(double)rand()/RAND_MAX));
    return 0;
}

Guess you can use 'time' and measure the time spent in 'program', and then figure out how long the sleep will be.

-Bob-

jlinkels · 03-28-2009, 03:47 PM

Look at this post of mine:
http://www.linuxquestions.org/questi...-timer-714154/

But there is a syntax error in my code, it was corrected in the succeeding post.

jlinkels