I have different script executed by the crontab.
The crontab is like this:
10,20,40,50 23,00-06 * * * /tmp/script1.bash
0,30 * * * * /tmp/script1.bash
*/2 * * * * /tmp/script2.bash
I want to run the two script in a way that I'm sure that the other script is not running, so if the script1 is triggered the script2 has to wait for script1 to finish.
I can't use a wait for the other process to finish because it can cause a starvation...
I would like to find a way in which every time the cron is triggered it adds the script to a queue and then the scripts are executed sequentially.
Which is the best way using only bash?
At the moment I found a solution using flock and exclusive locking mechanism, it should assure a FIFO behavior in terms of execution – Kerby82
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This question already has answers here:
Running a cron every 30 seconds
(21 answers)
Closed 4 years ago.
I have a php script that i need to run every 4 seconds for one hour a day, what is the best way to do this. I look up a way of using cron and sleep and also watch but what would be the best way of doing this over all?
Watch
watch -n10 command args
cron:
* * * * * /foo/bar/your_script
* * * * * sleep 4; /foo/bar/your_script
* * * * * sleep 8; /foo/bar/your_script
* * * * * sleep 12; /foo/bar/your_script
In short, it seems there isn't a simple way to do this using cron, since cron has a granularity of 60 seconds. Basically you would have to find a workaround.
One workaround, that you seem to have already come across, is to have multiple events with offset start times. E.g. Running a cron every 30 seconds
Another is to do more granular scheduling within the PHP script itself. E.g. In this answer
At that point it might make sense to then also make your PHP script a daemon process: Run php script as daemon process
I need to poll after deployment immediately i.e 0 seconds and then for every 45 mins using cron
Should poll as follows:: 00:00, 00:45, 1:30,2:15,3:00 and so on
Why do you have to use cron?
Your best bet in this case is to not use cron, rather use Mule's in-built fixed-frequency scheduler:
Note how the the default delay is "0" which means that it will run immediately upon deployment, then will run every 45 minutes after.
Here is the configuration-xml:
...
<flow name="polling-frequency-example-flow"
processingStrategy="synchronous">
<poll doc:name="poll-every-forty-five-mins">
<fixed-frequency-scheduler frequency="45" timeUnit="MINUTES"/>
</poll>
<!-- Do Something -->
</flow>
...
I don't know how to poll in Mule, but I can help you with your cron schedule.
Cron doesn't support every-45-minutes. You'll have to break it into three cronjobs:
0,45 0-23/3 * * *
30 1-23/3 * * *
15 2-23/3 * * *
CRON expression to poll every 45 minutes, this will solve ur first problem.
0 0/45 * 1/1 * ? *
Running once immediately after the deployment can't be handled with "Poll" as far as I know. As a workaround, in addition to the Poll component above, create another flow with "QUARTZ Inbound Endpoint" and it has a repeatCount attribute which you can set it to "Zero"(this will run exactly once and won't repeat itself).
Cron expression (for every 45 mins): 0 0/45 * 1/1 * ? *
If you want to run every 45 mins(00:15,01:00 like this) use quartz.
if you used poll operation it will not run every 45 mins, it will run every 45 mins when the project or flow deployed.
Simply use the fixed frequency scheduler construct as stated by #Mooz and then get the current time, check if it is a Sunday and do not process if it is. A cron expression is not really directly intended to handle all of the constraints of running immediately, a frequency relative to starting time rather than a clock schedule, and a day scheduling even with Mule's extensions to cron. Other solutions would be to use two controllers, but this would seem cleaner to me.
run every 10 seconds
0/10 * * * * ?
run every 45 minutes
* 0/45 * * * ?
Instead of using the Cron jobs just go with fixed frequency scheduler simply.
set the value as follows:
frequency: 45
start delay as :0
Time unit as:minutes
I'm using perl cron, and I want to make a rule like this
run every xx min/hours starting at yy:yy time (until the end of time)
How would I put this into a cron string? perl:cron seems to use the same syntax as regular cron so a regular cron string should work
TIA!
The short answer is that you will either need to write this yourself or find a different third-party package, due to your requirements. There's two things you're asking for that cron doesn't do:
Run every X minutes.
Say you want to run every 40 minutes, and you write this */40 * * * *. This actually runs every 60 minutes at 1:40, 2:40, etc.
Start/Stop at time Y/Z.
There's simply no cron syntax for this. You could use a couple more cronjobs to add/remove the main cronjob at the specified times, but this smells a lot like self-modifying code. Given the complexity (read: unreliability), it's probably better to find a different system.
You can specify intervals with a slash. Here's every 5 minutes:
*/5 * * * *
This is every 2 hours:
0 */2 * * *
You cannot give a start/ end time in cron.
I have two cronjobs, each using a "*/5 * * * *" schedule.
What I really want is to execute them every ten minutes, but the second one 5 minutes later than the first one.
Is there an elegant way to do this?
How about:
*/10 * * * * firstcommand
5-55/10 * * * * secondcommand
This works with at least one cron daemon---Dillon's cron, which I'm the current dev of. Whether it works on Vixie cron, or fcron, or bcron, or whichever cron daemon you happen to be using, I can't say.
Have your first cron task call at, which allows you to schedule a one-off execution at a specific time.
How would I get a cron job to run every 72 minutes? Or some not so pretty number like that?
Since cron runs jobs time-based, not interval-based, there's no blindingly simple way to do it. However, although it's a bit of a hack, you can set up multiple lines in crontab until you find the common denominator. Since you want a job to run every 72 minutes, it must execute at the following times:
00:00
01:12
02:24
03:36
04:48
06:00
07:12
...
As you can see, the pattern repeats every 6 hours with 5 jobs. So, you will have 5 lines in your crontab:
0 0,6,12,18 * * * command
12 1,7,13,19 * * * command
24 2,8,14,20 * * * command
36 3,9,15,21 * * * command
48 4,10,16,22 * * * command
The other option, of course, is to create a wrapper daemon or shell script that executes and sleeps for the desired time until stopped.
Use at (man at). Have your app or startup script calculate a startup time 72 minutes in the future and schedule itself to run again before it starts working.
Available on windows xp and vista too.
Here's an example for gnu/linux: at -f command.sh now + 72 minutes
You could always take the approach of triggering cron every minute, and having your script exit out immediately if it's been run more recently than 72 minutes ago.
Don't use cron...
#!/bin/sh
while [ true ]
do
sleep 4320
echo "Put your program here" &
done
You cannot directly do this from cron/crontab.
Cron jobs are run on a specific schedule, not on a specific interval.
One alternative would be to work out a schedule that approximated your "every 72 minutes" by running at midnight, 1:12, 2:24, 3:36, ..., and stretching it out to approximate hitting up at midnight. Your crontab file could specify all of these times as times to execute.
Another alternative would be to have a separate application handle the scheduling, and fire your application.
You'll need to set exactly 20 tasks for this - i.e. set one at 00:00, next one at 01:12, next one at 02:24, etc.
20 iterations make a full day.
Unfortunately, this is the only way to do it, as cron tasks are set up in a fixed schedule beforehand instead of being run, say, "after X minutes the last task was executed".
Uh I know this is long overdue, but I was looking at some scheduling issues and saw this question.
Just do this in your crontab
*/72 * * * * /home/script.sh