Controlling time stamps in a bash script


 
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# 1  
Old 06-06-2016
Controlling time stamps in a bash script

Hi,
I have a bash script that generates CSV (.txt) files at fairly regular time intervals. I'm currently time stamping each batch of measurements at the time I write the rows into a MySQL database. As the result, one set of data might get the time 12:01:32 and the next set of data gets the time 12:03:14. The average time between measurements is about 1-3 minutes.

This works fine, but I'm working on a frontend where I want to display measurements from various events in the same graphs, and the resolution should be 5 minutes.

So my script should ideally only kick off a new measurement every 5th minute and when it stores the times it should also be at even 5-minute intervals.

Some pseudo code showing the current behavior if it explains better:

Code:
#!/bin/bash

while true
do

   # Code to generate csvFile.txt. Should be initialized every 5th min.

   # Below is how I currently time stamp the rows in the database
   # Here I want the time given at fixed 5 minute intervals
   awk -v A="$(date "+%y%m%d  %T")"  '{print A,$0}' csvFile.txt | tr -s ' ' 
   ';' > csvFileToDB.txt

   # Code to inser the resulting files to MySQL not shown here
 fi
done

To summarize the wanted behavior with an example:

The script starts a new measurement at a fixed 5-minute interval. For example, one interval should start at 12:00. It then generates the CSV file (it normally takes one to two minutes) and stores the values to the database with the start time for the interval (in this case 12:00). Then the script waits until 12:05 before it starts over with the same procedure again.

Anyone who knows how to do this?

Thanks
//Z
# 2  
Old 06-06-2016
Use cron to run things you're scheduling regularly, put it in your crontab(crontab -e) like this:

Code:
0-59/5 * * * * /path/to/script.sh

Edit your cron table with cron -e. If you get errors, try setting a more complete PATH in your script.
This User Gave Thanks to Corona688 For This Post:
# 3  
Old 06-06-2016
Can you insert a sleep command into the loop? If it kicked off a background job every five minutes, sleep 300 would do the job. If every five minutes was a definite goal, code to create a time five minutes from now could be put into a script variable, then you would start your procedure. After that procedure, another loop that would only sleep for 1 second would wait for the target time to catch up.
If exactly five minutes is not that critical, just sleep for 3.5 minutes (tweak as needed) before starting over.
This User Gave Thanks to wbport For This Post:
# 4  
Old 06-06-2016
Thanks for suggestions. I need this to happen at exactly 5 min intervals as I have other databases with values also from each 5 min and I want to be able to print data from different tables in the same graphs. So the times have to be aligned (means 'sleep' is out of question). I will read up on crontab and see if it does the trick.
# 5  
Old 06-06-2016
That's pretty much what cron already does for you -- sleeps an exact interval, corrects, and runs your program.
This User Gave Thanks to Corona688 For This Post:
# 6  
Old 06-07-2016
Ok, tested and that was EXACTLY what I wanted to achieve. Thanks a lot Corona688! Smilie
This User Gave Thanks to Zooma For This Post:
# 7  
Old 09-27-2016
Crontab does not start

Back to this one again. Tried to automate a script called getStats.sh that looks like this:

Code:
#!/bin/bash
./startMeasuring.sh
./collectStats.sh

I go to crontab -e and add this line:
Code:
0-59/5 * * * * /usr/Measurements/getStats.sh

The problem is that nothing happens. I have tried to reboot the computer, but the scheduled task never starts.

Does someone know what the problem is? Or do you know how to figure it out through logs etc?

Cheers/Z
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