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You can set your Mac OS X account to automatically lock the screen so that the password is required after a certain amount of time of inactivity, but can you do the same thing using a schedule (say at 5:30 PM every day)? Kind of like how you can have the computer turn on/off or go to/wake up from sleep at a certain time.

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up vote 3 down vote accepted

You can use launchd to do this. Place the following xml into a new text file in ~/Library/LaunchAgents/ and call it something descriptive with a suffix of .plist. For example, mine is ~/Library/LaunchAgents/logoutAt1730.plist.

<?xml version="1.0" encoding="UTF-8"?>
    <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "">
    <plist version="1.0">
        <string>Logout At 5:30 PM</string>
            <string>/System/Library/CoreServices/Menu Extras/</string>

If you want it to run on the current power cycle (Eg you don't want to restart for this to take effect) use launchctl load ~/Library/LaunchAgents/logoutAt1730.plist to tell launchd about the new item. It should load automatically next time you login.

Use launchctl list and look for the label string (Logout at 5:30 PM) to validate that launchd knows about the item.

I have verified this works on my workstation. I don't know why cron doesn't.

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Yes, that worked, thanks! Just named the file suspend instead of logout. Now I just need to get user confirmation with a popup, if that's possible--I'll open another question: – newenglander Apr 28 '12 at 19:49
New question came up here, FYI: – newenglander May 10 '12 at 17:20

EDIT: Although I am not certain of why cron fails to work for this specific use-case, this answer is superceeded by the (currently more correct) answer using launchd.

Use crontab -e in the terminal application to add /System/Library/CoreServices/Menu\ Extras/ -suspend to the Crontab at the appropriate time, like so (for 5:30 PM):

30 17 * * * /System/Library/CoreServices/Menu\ Extras/ -suspend

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Thanks for the tip, it doesn't work for me, but that's another question. (Shouldn't it be 17 instead of 7 for 5 PM?) – newenglander Apr 22 '12 at 7:48
Ah yeah I did it on the fly. Good eye. I just tried the /System/Library/CoreServices/Menu\ Extras/ -suspend command by itself and it worked. what OS are you running? – zwerdlds Apr 22 '12 at 17:12
Lion. The command itself worked by itself for me too, but I tried setting a crontab with a time a few minutes in the future and nothing happened when the specified time came. – newenglander Apr 23 '12 at 18:36
Hmm, I'm experiencing the same issue. I'll look into it tonight. Perhaps it would work as a script? – zwerdlds Apr 23 '12 at 18:56
No luck there. I think the user running the cronjobs (root) can't call suspend on another user, at least not with this command. – newenglander Apr 24 '12 at 19:02

I wanted something similar, but instead of always locking at a specific time, I wanted to lock only on certain conditions. The script I used to check those conditions was triggered by cron, so I had the same issue.

When I tried CGSession -suspend in a cronjob, and noticed that when it was triggered, logged an error, saying only root and the current logged user could trigger a Fast User Switching. So my solution: run it as root.

So in my script, I used the following, to lock the computer:

sudo /usr/bin/osascript -e 'tell application "System Events" to do shell script "/System/Library/CoreServices/Menu\\ Extras/ -suspend"'

Convoluted? Yes. Working? Positive!

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Using sudo .../CGSession -suspend directly (without using AppleScript) didn't work either then? – patrix Apr 19 '13 at 17:45
Yeah, it didn't. No idea why. – Guillaume Boudreau Apr 19 '13 at 18:44

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