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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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2  
Which OS X version? – patrix♦ Aug 30 '12 at 20:47

4 Answers

up vote 16 down vote accepted

In Mountain Lion you can use the caffeinate command.

caffeinate -u -t 1000

will prevent idle sleep for 1000 seconds.

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up vote 3 down vote

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 – binarybob Aug 31 '12 at 9:21
@binarybob Oh! I didn't know that. Thanks for the tip! – daviesgeek Aug 31 '12 at 14:26
@davisgeek - really nice! Thanx for the tip. – kobame Sep 3 '12 at 11:45
@kobame Yup. NP. That's what we're here for! :-) – daviesgeek Sep 3 '12 at 17:48
up vote 5 down vote

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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2  
See also man screen. – mankoff Sep 1 '12 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. ;) – kobame Sep 3 '12 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. – kobame Sep 3 '12 at 11:43
@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. – ephsmith Sep 3 '12 at 13:31
@kobame, did any of these answers solve your problem? – ephsmith Sep 3 '12 at 13:32
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up vote 3 down vote 
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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