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Full Discussion: Shell Script to Delete Old Cron Jobs
Top Forums Shell Programming and Scripting Shell Script to Delete Old Cron Jobs Post 302786889 by AndrewT on Thursday 28th of March 2013 02:04:03 PM
Old 03-28-2013
Shell Script to Delete Old Cron Jobs
I have a cron entry to deploy a website portal from a staging server to a series of production servers on a weekly basis.

On occasion, a random office worker who knows nothing about Linux let alone cron, will be tasked to update news picks on the staging server and then run a manual deployment to the production servers. So I threw together a quick PHP/JQuery script that will take the date and time chosen and insert a properly-formatted line into cron.

The trouble I'm having is finding a way to clean out the old one-run cron jobs. Rather than having the sys admin go in once in a while to clean out those old jobs, I'd like to have it deleted at the end of the run. It will take nearly an hour for the deployment to complete, so comparing the minutes passed will be enough.

What I want to do is using a bash script, read in a crontab line, find all lines with specific numbers for the date/time (no '*', ranges, multiples or '*/n'), and compare them to the current date. If in the past, delete the line.

Note there are lines that are comments or variable declarations, as well as the weekly deployment.

Any ideas?

Thanks,
Andrew

---------- Post updated at 01:04 PM ---------- Previous update was at 09:47 AM ----------

Nevermind, got it figured out. Bit of a hack but...

Code:
currYear=$(date '+%Y')
cronNow=$(date '+%Y-%m-%d %H:%M')
cronNowS=`date --date="$cronNow" +%s`
crontab -l > tempcron.txt
touch temp
while read -r line ; do
        #parse the line into an array by space
        IFS=' ' read -a cronJob <<< "$line"
        minute="${cronJob[0]}"
        hour="${cronJob[1]}"
        day="${cronJob[2]}"
        month="${cronJob[3]}"
        #if it's anything but numeric, it's not a single date...
        cronNumTest=$minute$hour$day$month
        if [[ $cronNumTest =~ ^[0-9]+$ ]]; then
                #numeric: convert to a date and compare to now.
                cronTime="$currYear-$month-$day $hour:$minute"
                cronTimeS=`date --date="$cronTime" +%s`
                if [[ $cronTimeS -gt $cronNowS ]]; then
                        echo "$line" >> temp
                fi
        else
                #leave the CONST declarations, comments and permanent cron jobs intact...
                echo "$line" >> temp
        fi
done < "tempcron.txt"
mv temp tempcron.txt
crontab < tempcron.txt
rm tempcron.txt

If anyone has a shorter, cleaner solution, I'd appreciate seeing your example code.

Cheers,
Andrew
Last edited by AndrewT; 03-28-2013 at 03:11 PM..
 

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LEARN ABOUT X11R4

queuedefs

queuedefs(4)							   File Formats 						      queuedefs(4)

NAME

       queuedefs - queue description file for at, batch, and cron

SYNOPSIS

       /etc/cron.d/queuedefs

DESCRIPTION

       The queuedefs file describes the characteristics of the queues managed by cron(1M). Each non-comment line in this file describes one queue.
       The format of the lines are as follows:

	      q.[njobj][nicen][nwaitw]

       The fields in this line are:

       q	The name of the queue. a is the default queue for jobs started by at(1); b is the default queue for jobs  started  by  batch  (see
		at(1)); c is the default queue for jobs run from a crontab(1) file.

       njob	The  maximum  number of jobs that can be run simultaneously in that queue; if more than njob jobs are ready to run, only the first
		njob jobs will be run, and the others will be run as jobs that are currently running terminate.  The default value is  100.

       nice	The nice(1) value to give to all jobs in that queue that are not run with a user ID of super-user.  The default value is 2.

       nwait	The number of seconds to wait before rescheduling a job that was deferred because more than njob jobs were running in  that  job's
		queue, or because the system-wide limit of jobs executing has been reached.  The default value is 60.

       Lines beginning with # are comments, and are ignored.

EXAMPLES

       Example 1: A sample file.

       #
       #
       a.4j1n
       b.2j2n90w

       This  file  specifies that the a queue, for at jobs, can have up to 4 jobs running simultaneously; those jobs will be run with a nice value
       of 1.  As no nwait value was given, if a job cannot be run because too many other jobs are running cron will wait 60 seconds before  trying
       again to run it.

       The  b  queue, for batch(1) jobs, can have up to 2 jobs running simultaneously; those jobs will be run with a nice(1) value of 2.  If a job
       cannot be run because too many other jobs are running, cron(1M) will wait 90 seconds before trying again to run it. All	other  queues  can
       have up to 100 jobs running simultaneously; they will be run with a nice value of 2, and if a job cannot be run because too many other jobs
       are running cron will wait 60 seconds before trying again to run it.

FILES

       /etc/cron.d/queuedefs	       queue description file for  at, batch, and  cron.

SEE ALSO

       at(1), crontab(1), nice(1), cron(1M)

SunOS 5.10							    1 Mar 1994							      queuedefs(4)
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