So my problem is the following, I need to run a job (lets call it job-A) every minute, but before it can be executed I need to start a server and do other things. I mean, once all those executions are done I need to run job-A every minute.
My crontab looks like this:
@reboot first-required-job.sh
@reboot second-required-job.sh
@reboot third-required-job.shMy idea is to let the first execution of job-A start 5 minutes after boot, to be sure that all the previous processes are done, and then run every minute.
If I do something like
@reboot (sleep 300; job-A.sh)it will only run once after boot.
There must be a simple way to do this, but I can't figure it out. How can I do this??
01 Answer
There must be a simple way to do this
In my point of view, your sleep 300 solution is already a simple way. It's not clean, because the other jobs might take longer than 300 seconds. But it's a simple way.
My idea for a clean solution is to let the other scripts create a file once they are done. This way the job-A is able to find out if the precondition is met, just by checking the existence of that file.
I would wrap the other 3 scripts into a new script, eg. job-A-preconditions.sh. That Script would look like this:
#!/bin/bash
/path/first-required-job.sh
/path/second-required-job.sh
/path/third-required-job.sh
touch "/tmp/very-unique-filename-to-signal-job-A-can-start"The crontab would look like this:
# run the preconditions job only once after boot
@reboot /path/job-A-preconditions.sh
# run job-A every minute
* * * * * test -f "/tmp/very-unique-filename-to-signal-job-A-can-start" && /path/job-A.shNote: It's important that the signal file gets deleted automatically, before the precondition jobs start. This happens automatically if your /tmp/ uses tmpfs (aka ramdrive). If you have systemd-tmpfiles-clean.service enabled, /tmp/ gets cleaned before shutdown, so this works too.
Another note: The deluxe version would be to use systemd for all jobs involved, and just use the depency mechanism of systemd.
