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I have a long running script at the remote computer.

I don't want terminate my ssh session, and need enter it into a shell script.

How is it possible to prevent my Mac from falling into sleep from the command line?

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    Which OS X version? Commented Aug 30, 2012 at 20:47

7 Answers 7

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In Mountain Lion you can use the caffeinate command.

caffeinate -u -t 1000

will prevent idle sleep for 1000 seconds.

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    I've had no success yet with any 'caffeinate' cmdline combination (including one above) nor Caffeine.app in Mavericks preventing sleep upon lid close. InsomniaX.app is only thing that has thus far prevented lid sleep, but haven't yet found a working cmdline version (haven't yet made michaelgoerz.net/blog/2009/09/… work - it may be obsolete). Even still, I want something that enables display-password requirement even while denying sleep for limited, programmable time upon lid close...and InsomniaX.app doesn't appear to do that either. Commented Feb 11, 2014 at 20:08
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    Similar issues. I am on Yosemite, and even though I run caffeinate in terminal, after a while the screen goes dark, and I have to log back in. This suggests to me that caffeinate isn't keeping the Mac awake, which is my goal so that the Wifi connection can persist / whatever I have going on can proceed. Commented Jan 12, 2015 at 3:39
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The solution to this problem is not keeping the client (your Mac) awake. Using approaches like this are undependable. What happens if the network connection is lost? Even if your Mac is awake, the script will halt.

Use nohup

If your long-running script is called eternity.sh, try the following:

nohup /path/to/eternity.sh > /path/to/output.out &

Now you can even close the connection and your script will keep running. The & backgrounds the process so you can keep the connection open and enter commands. View any output from your script via:

tail -f /path/to/output.out

The paths in the examples are optional if the script is on your path and you want script output to be written to output.out in the current directory.

I manage scripts that run for days at a time. Scripts like these should be detached from the terminal. Thankfully, nohup provides an easy-to-remember command invocation to achieve this--think no hangup.

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    See also man screen. Commented Sep 1, 2012 at 6:20
  • @mankoff - i'm already using screen. It is the best command since the dicovery of a sliced breed. ;) The main point of the question is eleiminate the need of the "ssh to@somewhere" when my mac fall asleep - I simply don't want terminate my ssh session - my command on the remote side is already "protected" with screen. ;) Commented Sep 3, 2012 at 11:40
  • @ephsmith - the question was: how to eliminate the ssh session terminate... ofc nohup is nice for situations when your remote command is not an interactive one. For the interactive commands the screen is much much better solution. Thanx anyway for reply. Commented Sep 3, 2012 at 11:43
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    @kobame, maybe the point of the question and this additional information should've been included in your original question. The first line in your question referred to a long running script. I assumed it wasn't interactive which led to the reference to nohup. Commented Sep 3, 2012 at 13:31
  • @kobame, did any of these answers solve your problem? Commented Sep 3, 2012 at 13:32
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Another option is pmset. Use the command pmset noidle to prevent sleep as long as pmset is running. Unfortunately, it requires a separate Terminal window with pmset running in it. However, the other option, caffeinate, only lets you set a certain time. So it's a matter of choosing whether you want to open a second SSH session, or deal with a time restraint.

Edit: According to binarybob's comment, you can actually run it in the background like this: pmset noidle & To get back to pmset type fg.

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    You can also run pmset in the background using pmset noidle & and therefore continue using the current command prompt. Type fg to get pmset back, at which point you can Ctrl+C it Commented Aug 31, 2012 at 9:21
  • @binarybob Oh! I didn't know that. Thanks for the tip! Commented Aug 31, 2012 at 14:26
  • @davisgeek - really nice! Thanx for the tip. Commented Sep 3, 2012 at 11:45
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    this one also works in IPython notebook: !pmset noidle -- very nice when you have a desktop serving IPython notebook and a laptop connecting remotely. Commented Nov 20, 2016 at 16:18
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    This doesn't work for me. It runs successfully, the message "Preventing idle sleep (^C to exit)..." appears, but it still goes to sleep. Commented Dec 7, 2017 at 13:56
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caffeinate -i -s /bin/ssh ...

Explanation:

-i - Prevent idle sleep.

-s - Prevent system sleep (entirely, even if you close the lid). Note: it only works while on AC power.

/bin/ssh - Just keep writing the command you want to execute. Using ssh directly instead of /bin/ssh should also work.

Results: Your system will not sleep as long as the ssh command is running.

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I find that for macOS 13, Ventura, sudo pmset sleep 0 will change the Settings > Displays > Advanced > Energy > Prevent automatic sleeping when the display is off, to enabled.

Similarly, setting it to anything other than 0 will disable that setting (and presumably change some value elsewhere).

You have to exit and restart settings to observe the change - it doesn't update as soon as the pmset command has run.

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  • On portable computers, the setting is "Prevent automatic sleeping on power adapter when the display is off", and appears to be set with pmset -c sleep 0. Commented Apr 25, 2023 at 19:35
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If you are looking for the nuclear option like I was:

sudo systemsetup -setcomputersleep Never

–Set or Disable Sleep Due to Mac System Inactivity from the Command Line in OS X

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    This is out of date. For Ventura, pmset sleep 0 Commented Apr 5, 2023 at 22:17
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use caffeinate.

the installed policies on my machine make everything dependent on the display, so the only thing that worked for me was to invoke caffeinate with the -d option.

$ caffeinate -d

excerpt from the man page:

CAFFEINATE(8) NAME caffeinate – prevent the system from sleeping on behalf of a utility SYNOPSIS caffeinate [-disu] [-t timeout] [-w pid] [utility arguments...] DESCRIPTION caffeinate creates assertions to alter system sleep behavior. If no assertion flags are specified, caffeinate creates an assertion to prevent idle sleep. If a utility is specified, caffeinate creates the assertions on the utility's behalf, and those assertions will persist for the duration of the utility's execution. Otherwise, caffeinate creates the assertions directly, and those assertions will persist until caffeinate exits. Available options: -d Create an assertion to prevent the display from sleeping.
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