##osx-server

G'day.

hi.

If two processes chmod a file at the same time what happens? The calls are serialized or chmod returns an error?

One is gonna win. Which one wins is unknown. "Race condition."

So the 'loser' returns an error?

Nope, the last chmod wins, assuming it actually has the necessary rights to execute successfully.

This behavior is defined by posix or something

?

I doubt it.

What makes you expect it to work that way?

With the Morgan, err, rum, I mean El Capitan, How does one fix user permissions if they happen to go under water? diskutil /repairPermissions is no longer a thing in 10.11... Thoughts/ideas?

burzos: It's like asking which of your two children will eat the last cookie. It's a race. Maybe the oldest gets there because s/he is the fastest. Maybe the youngest gets there first because the oldest fell down while running to the cookie jar. Too many variables are in play to give a solid answer to your question beyond "it depends".

Their diskutil first aid does not fix user perms, only system files with receipts.

I guess, theoretically, the first chmod might lock the file while it changes the rights, if the second checked the file then it might throw an error about locked or something like that. But I think that's doubtful

burzos nronksr: You may find more traffic/people at MacAdmins Slack, http://macadmins.org

foigus: When I let two processes modify the uid/gid of the same file simultaneously, sometimes the uid/gid show as '_update_sharing'?

Know anything about that?

# id _update_sharing

uid=95(_update_sharing) gid=4294967294(nobody) groups=4294967294(nobody),12(everyone),61(localaccounts),98(_lpadmin),100(_lpoperator),701(com.apple.sharepoint.group.1)

It's a defined user on the computer, why it lands there, I don't know

I'll take a look foigus. thanks.

Thanks foigus

Question for the collective, is launchd supposed to be so inaccurate?

I set a job up, and it runs ~20 seconds after the time it is set.

Define "inaccurate"?

Anything in the log that might give you a hint as to what it did?

My computer hardware class is making a bell system with some old Minis, but launchd doesn't launch exactly on the minutes.

I haven't had that personal experience. Is the launchd running a script, or calling a command?

Nothing in the log. Running a script.

I went back to cron, and it fires immediately on the minute.

I found this discussion: https://discussions.apple.com/thread/5137946?ts... but no solution.

I've had pretty good luck with timing