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Linux is a family of open source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991 by Linus Torvalds. Linux is typically packaged in a Linux distribution (or distro for short).

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(Solved) How do I make flock ignore a nohup process? (lemmy.world)

submitted 2 days ago* (last edited 2 days ago) by Gonzako@lemmy.world to c/linux@lemmy.ml

7 comments fedilink hide all child comments

Hi!

I've a cronjob that I don't want to be concurrent but it needs to leave a long-running process after it does it's job that I set up with a nohup command.

The deal is that once the script has setup the lock doesn't get released so any further calls to the script just get ignored.

Is there a better alternative/flag I'd use? I couldn't discern much from the flock or nohup man pages.

Solved: With bit more fiddling found the - u flag on the flock man page. You can unlock yourself at the very end of the script.

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[–] hades@feddit.uk 3 points 2 days ago (1 children)

Can you modify the script to release the lock after the process has started?

[–] Gonzako@lemmy.world 2 points 2 days ago

Yes! I found the - u flag on flock and that got it working. Thanks for the attention anyway.

[–] Frid0lin@feddit.org 2 points 2 days ago (1 children)

Could you just save the pid of that cronjob in a file? (Assuming this cronjob calls bash script). Before the next run of the cronjob check if that process with that pid is still running? Hoping, I understand your problem correctly. You do not want to run the cronjob again until the first run finishes?

[–] Gonzako@lemmy.world 2 points 2 days ago (1 children)

Flock does this functionality, the deal is that it waited for the long-running process to end so it wouldn't release the lock after the script was done. Adding a line manually releasing it fixed it.

It's an auto-update script, you don't wanna start a new update while one is underway.

[–] Frid0lin@feddit.org 2 points 2 days ago (1 children)

Thanks for the update maybe I'm a bit oldschool and need to dig deeper "in the flock" ;-)

[–] Gonzako@lemmy.world 2 points 2 days ago (1 children)

sorry fLock it my phone doesn't like it and don't really know what the f stands for. but flock is a Linux command that let's you manage simple concurrency issues https://www.man7.org/linux/man-pages/man1/flock.1.html

[–] Badabinski@kbin.earth 2 points 2 days ago

the f stands for file. The c manpage has some details on how it works: https://www.man7.org/linux/man-pages/man2/flock.2.html