• Uncategorized

About automation : CRON-job-to-run-on-the-last-day-of-the-month

Question Detail

I need to create a CRON job that will run on the last day of every month.
I will create it using cPanel.

Any help is appreciated.
Thanks

Question Answer

Possibly the easiest way is to simply do three separate jobs:

55 23 30 4,6,9,11        * myjob.sh
55 23 31 1,3,5,7,8,10,12 * myjob.sh
55 23 28 2               * myjob.sh

That will run on the 28th of February though, even on leap years so, if that’s a problem, you’ll need to find another way.


However, it’s usually both substantially easier and correct to run the job as soon as possible on the first day of each month, with something like:

0 0 1 * * myjob.sh

and modify the script to process the previous month’s data.

This removes any hassles you may encounter with figuring out which day is the last of the month, and also ensures that all data for that month is available, assuming you’re processing data. Running at five minutes to midnight on the last day of the month may see you missing anything that happens between then and midnight.

This is the usual way to do it anyway, for most end-of-month jobs.


If you still really want to run it on the last day of the month, one option is to simply detect if tomorrow is the first (either as part of your script, or in the crontab itself).

So, something like:

55 23 28-31 * * [[ "$(date --date=tomorrow +\%d)" == "01" ]] && myjob.sh

should be a good start, assuming you have a relatively intelligent date program.

If your date program isn’t quite advanced enough to give you relative dates, you can just put together a very simple program to give you tomorrow’s day of the month (you don’t need the full power of date), such as:

#include <stdio.h>
#include <time.h>

int main (void) {
    // Get today, somewhere around midday (no DST issues).

    time_t noonish = time (0);
    struct tm *localtm = localtime (&noonish);
    localtm->tm_hour = 12;

    // Add one day (86,400 seconds).

    noonish = mktime (localtm) + 86400;
    localtm = localtime (&noonish);

    // Output just day of month.

    printf ("%d\n", localtm->tm_mday);

    return 0;
}

and then use (assuming you’ve called it tomdom for “tomorrow’s day of month”):

55 23 28-31 * * [[ "$(tomdom)" == "1" ]] && myjob.sh

Though you may want to consider adding error checking since both time() and mktime() can return -1 if something goes wrong. The code above, for reasons of simplicity, does not take that into account.

There’s a slightly shorter method that can be used similar to one of the ones above. That is:

[ $(date -d +1day +%d) -eq 1 ] && echo "last day of month"

Also, the crontab entry could be update to only check on the 28th to 31st as it’s pointless running it the other days of the month. Which would give you:

0 23 28-31 * * [ $(date -d +1day +%d) -eq 1 ] && myscript.sh

What about this one, after Wikipedia?

55 23 L * * /full/path/to/command

Adapting paxdiablo’s solution, I run on the 28th and 29th of February. The data from the 29th overwrites the 28th.

# min  hr  date     month          dow
  55   23  31     1,3,5,7,8,10,12   * /path/monthly_copy_data.sh
  55   23  30     4,6,9,11          * /path/monthly_copy_data.sh
  55   23  28,29  2                 * /path/monthly_copy_data.sh

For AWS Cloudwatch cron implementation (Scheduling Lambdas, etc..) this works:

55 23 L * ? *

Running at 11:55pm on the last day of each month.

Set up a cron job to run on the first day of the month. Then change the system’s clock to be one day ahead.

You could set up a cron job to run on every day of the month, and have it run a shell script like the following. This script works out whether tomorrow’s day number is less than today’s (i.e. if tomorrow is a new month), and then does whatever you want.

TODAY=`date +%d`
TOMORROW=`date +%d -d "1 day"`

# See if tomorrow's day is less than today's
if [ $TOMORROW -lt $TODAY ]; then
echo "This is the last day of the month"
# Do stuff...
fi

For a safer method in a crontab based on @Indie solution (use absolute path to date + $() does not works on all crontab systems):

0 23 28-31 * * [ `/bin/date -d +1day +\%d` -eq 1 ] && myscript.sh

Some cron implementations support the “L” flag to represent the last day of the month.

If you’re lucky to be using one of those implementations, it’s as simple as:

0 55 23 L * ?

That will run at 11:55 pm on the last day of every month.

http://www.quartz-scheduler.org/documentation/quartz-1.x/tutorials/crontrigger

#########################################################
# Memory Aid 
# environment    HOME=$HOME SHELL=$SHELL LOGNAME=$LOGNAME PATH=$PATH
#########################################################
#
# string         meaning
# ------         -------
# @reboot        Run once, at startup.
# @yearly        Run once a year, "0 0 1 1 *".
# @annually      (same as @yearly)
# @monthly       Run once a month, "0 0 1 * *".
# @weekly        Run once a week, "0 0 * * 0".
# @daily         Run once a day, "0 0 * * *".
# @midnight      (same as @daily)
# @hourly        Run once an hour, "0 * * * *".
#mm     hh      Mday    Mon     Dow     CMD # minute, hour, month-day month DayofW CMD
#........................................Minute of the hour
#|      .................................Hour in the day (0..23)
#|      |       .........................Day of month, 1..31 (mon,tue,wed)
#|      |       |       .................Month (1.12) Jan, Feb.. Dec
#|      |       |       |        ........day of the week 0-6  7==0
#|      |       |       |        |      |command to be executed
#V      V       V       V        V      V
*       *       28-31   *       *       [ `date -d +'1 day' +\%d` -eq 1 ] && echo "Tomorrow is the first today now is  `date`" >> ~/message
1       0       1       *       *       rm -f ~/message
*       *       28-31   *       *       [ `date -d +'1 day' +\%d` -eq 1 ] && echo "HOME=$HOME LOGNAME=$LOGNAME SHELL = $SHELL PATH=$PATH" 

00 23 * * * [[ $(date +'%d') -eq $(cal | awk '!/^$/{ print $NF }' | tail -1) ]] && job

Check out a related question on the unix.com forum.

You can just connect all answers in one cron line and use only date command.

Just check the difference between day of the month which is today and will be tomorrow:

0 23 * * * root [ $(expr $(date +\%d -d '1 days') - $(date +\%d)  ) -le 0 ]  && echo true

If these difference is below 0 it means that we change the month and there is last day of the month.

55 23 28-31 * * echo "[ $(date -d +1day +%d) -eq 1 ] && my.sh" | /bin/bash 

What about this?

edit user’s .bashprofile adding:

export LAST_DAY_OF_MONTH=$(cal | awk '!/^$/{ print $NF }' | tail -1)

Then add this entry to crontab:

mm hh * * 1-7 [[ $(date +'%d') -eq $LAST_DAY_OF_MONTH ]] && /absolutepath/myscript.sh

The last day of month can be 28-31 depending on what month it is (Feb, March etc). However in either of these cases, the next day is always 1st of next month. So we can use that to make sure we run some job always on the last day of a month using the code below:

0 8 28-31 * * [ "$(date +%d -d tomorrow)" = "01" ] && /your/script.sh

If the day-of-the-month field could accept day zero that would very simply solve this problem. Eg. astronomers use day zero to express the last day of the previous month. So

00 08 00 * * /usr/local/sbin/backup

would do the job in simple and easy way.

I found out solution (On the last day of the month) like below from this site.

 0 0 0 L * ? *

CRON details:

Seconds Minutes Hours   Day Of Month    Month   Day Of Week  Year
0       0       0       L               *       ?            *

To cross verify above expression, click here which gives output like below.

2021-12-31 Fri 00:00:00
2022-01-31 Mon 00:00:00
2022-02-28 Mon 00:00:00
2022-03-31 Thu 00:00:00
2022-04-30 Sat 00:00:00

Not sure of other languages but in javascript it is possible.

If you need your job to be completed before first day of month node-cron will allow you to set timezone – you have to set UTC+12:00 and if job is not too long most of the world will have results before start of their month.

Better way to schedule cron on every next month of 1st day

This will run the command foo at 12:00AM.

0 0 1 * * /usr/bin/foo

Be cautious with “yesterday”, “today”, “1day” in the ‘date’ program if running between midnight and 1am, because often those really mean “24 hours” which will be two days when daylight saving time change causes a 23 hour day. I use “date -d ‘1am -12 hour’ “

In tools like Jenkins, where usually there is no support for L nor tools similar to date, a cool trick might be setting up the timezone correctly. E.g. Pacific/Kiritimati is GMT+14:00, so if you’re in Europe or in the US, this might do the trick.

TZ=Pacific/Kiritimati \n H 0 1 * * 

Result: Would last have run at Saturday, April 30, 2022 10:54:53 AM GMT; would next run at Tuesday, May 31, 2022 10:54:53 AM GMT.

Use the below code to run cron on the last day of the month in PHP

$commands = '30 23 '.date('t').' '.date('n').' *';

You may also like...

Leave a Reply

Your email address will not be published.

This site uses Akismet to reduce spam. Learn how your comment data is processed.