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Many processes running at the same time


 
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# 1  
Old 02-12-2018
Many processes running at the same time

Hello everybody ,

I launched cron to execute a task every hour but the job takes more than hour that's why I'm getting more than 1000 cron processes running at the same time !!!
My question is how to tell cron not to execute unless the job terminated in order to have only one process running .
Thanks in advance
# 2  
Old 02-12-2018
Create your own 'flag'. For example, when the job finishes, the last thing it does is create a file called 'oktorun'. The first thing the job does when it starts is check for the existence of the file 'oktorun' and, if it does not exist then do nothing and terminate. If the file does exist then delete it and run the job. So the file does not exist whilst a job is running.

Anyway, if you're happy for a job to start immediately after the previous one finishes then why not get it to spawn itself (without the use of cron) ?

Last edited by hicksd8; 02-12-2018 at 08:42 AM..
This User Gave Thanks to hicksd8 For This Post:
# 3  
Old 02-12-2018
first of all I wanna thank you for your answer ,
but to be honest I have no idea how to create this file , where to put it and what should I put inside.
same for the second hypothesis
thanks
# 4  
Old 02-12-2018
Hmmm - something seems to be wrong here. 1000 jobs, started one per hour, would be 41 days worth of jobs - if not a single job finished in the meantime. Are you sure everything is correct with your script / program? Is it expected to finish in close to an hour? Does it finish at all? Are there locking problems?
This User Gave Thanks to RudiC For This Post:
# 5  
Old 02-12-2018
@RudiC......Good thinking.
@beautymind......Please post the script you are using.
# 6  
Old 02-12-2018
One example of using a flag, or lock file.
Code:
#!/bin/bash
myname=${0##*/}
if [[ -f /tmp/${myname} ]] 
then
    myname_proc=$(</tmp/${myname})
    if ps -p ${myname_proc} >/dev/null
    then exit
    else rm  /tmp/${myname} # assumption: last iteration of program died
    fi
fi
echo $$ > /tmp/${myname}
cleanup() {
    trap '' 0 HUP INT QUIT ABRT TERM # clear traps
    rm /tmp/${myname}
    # other cleanup here
}
trap 'cleanup' 0 # always run cleanup on exit
trap 'exit' HUP INT QUIT ABRT TERM # exit on one of these signals
# the rest of your script goes here

A good place to put such a file is the /tmp directory. The cleanup function should ensure that the file is deleted on exit, so you don't have to remember to put
Code:
rm /tmp/${myname}

everywhere you exit the program. Putting the PID in the file and then checking whether the process exists is optional, and there in case the program exits abnormally, leaving the file in place.

Andrew
This User Gave Thanks to apmcd47 For This Post:
# 7  
Old 02-12-2018
@RudiC , I don't know what is the problem because is it expected to finish in close to an hour.

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