I'm working on a new project and I would like to setup a cron to run every 6-8 hours at a random minute. Any suggestions on the best way to achieve this would be greatly appreciated.
Let's run the cron every 6 hours:
0 */6 * * * /path/to/script.sh
Now, in your bash script:
#!/bin/bash
maxdelay=$((2*60)) # 2 hours converted to minutes
delay=$(($RANDOM%maxdelay)) # a random delay
(sleep $((delay*60)); /path/to/script.sh) & # background a subshell to wait, then run the script
You can also use anacron for RANDOM_DELAY feature.
Related
I have to schedule execution of a .sh file for every 5 hours 30 minutes. is it possible to configure this way in linux crontab.
This should work. Also make sure your shell script should have valid permissions to exeucte.
30 */5 * * * sh yourscript
I have a script that I would like to run 60 seconds after initial system reboot and then every 10 minutes after that. I currently need two cron job listings to achieve this:
*/10 * * * * php myscript.php
#reboot /bin/sleep 60; php myscript.php
The first listing will run my cron job immediately after system boot and so I need to have the second listing to account for the on start wait time.
Is there anyway to combine the above two cron listings into one?
I want a cronjob to run every one hour randomly. (i.e if the first job runs at 58 minutes,the second job should run at 47 minutes and the third one at 52 minutes and so on) But this should run randomly for everyone hour. Is there a way to do this?
You could run a job every hour, on the hour, that sleeps up to 3,599 seconds and then executes your script:
0 * * * * /path/to/perl -e 'sleep int rand 3600' && /path/to/yourScript
Or, using PHP if you prefer that to Perl:
0 * * * * /path/to/php -r 'sleep(rand(0,3599));' && /path/to/yourScript
You can find the path to Perl with:
which perl
likewise for PHP:
which php
Instead of using perl or even php, just use the BASH $RANDOM built in divided by 3600 which equals one hour like so.
0 * * * * sleep $((RANDOM%3600)) && /path/to/yourScript
Keep in mind that you will probably have some race conditions with a script sleeps randomly close to an hour depending on how long it takes for your script to execute.
I need some help in writing a Linux script that do the following:
command 1
command 2
wait 10 minutes
command 3
command 4
and this script should run automatically at specific time for example 4 am...
Thank in advance
You can create a script.sh like:
#!/bin/bash
command 1
command 2
sleep 600 # 600 seconds = 10 min
command 3
command 4
And then create a cronjob:
0 4 * * * /bin/bash /path/to/script.sh
You can see more info of cron in https://stackoverflow.com/tags/cron/info
if you want the job to run once at a future time, instead of cron use at
at 4am tomorrow <<END
command 1
command 2
sleep 600
command 3
command 4
END
One of the advantages of at is that it will execute the commands using your current environment. The limited environment provided by cron is a cause of confusion for many people.
I want to set a cron run after an other cron. For example: Cron A finishs at 01:00 PM, cron B will start at 01:01 PM. The problem is I don't know when cron A finishs.
I checked the crontab syntax. It doesn't provide any param for that purpose.
My actual situation is:
# This cron must run first.
? ? * * * /usr/local/bin/php -f /path/select_and_print_to_log_file.php
# two these crons runs at the same time.
0 13 * * * /usr/local/bin/php -f /path/update_user.php
0 13 * * * /usr/local/bin/php -f /path/update_image.php
# This cron runs right after two above cron completes.
? ? * * * /usr/local/bin/php -f /path/select_and_print_to_log_file.php
You can use the batch command inside the first cron to have the second thing being scheduled to run.
Your first job could produce a timestamp when finished.
Then you estimate - for example - that job A needs about 60 to 90 minutes. After 60 minutes, you start job B. Job b looks for the timestamp. If it is present, job B starts, else it waits for a minute and looks again.
After finishing, job B deletes the timestamp, or renames it, maybe from 'todo' to 'done'. You could insert the current date inside the file, to check, whether your estimation is still acceptable, or should be adjusted.
What I do in such cases (commonly a backup scenario where I don't want to thrash the disk by having concurrent backups) is to write a script that cron calls, and in the script have the actual tasks run serially.
Something like:
#!/bin/bash
/usr/local/bin/php -f /path/update_user.php
/usr/local/bin/someOtherTaskToRunSecond
YMMV.