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What are the ways I can regain control over my computer when I have terminal in full screen mode and type:

cat /dev/random

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Why are you typing cat /dev/random? – Daniel Lawson♦ Sep 16 '12 at 3:57
@DanielLawson - I'm learning OSX and experimenting. I hope to learn how to recover from a runaway process, which may happen in a developer environment (which I'm in) – makerofthings7 Sep 16 '12 at 4:06
1  
You can press the power button and hold it. The filesystem is journaled and you'll soon learn which programs don't save their files cleanly :-/ – bmike♦ Sep 16 '12 at 18:55

2 Answers

up vote 4 down vote accepted

If you have Terminal.app open anyway (doesn't matter whether it's in fullscreen mode or not):

  • Cmd-T to create new tab/shell
  • ps aux | fgrep /dev/random to find the running cat (you can grep for cat as well but there might be more than one matching line)
  • kill <PID from above> (or kill -9 <PID>)

Just be patient, the system may be really slow (even on a multicore system as I've just found out).

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Is "kill -9" a joke referring to 9 lives of a cat, or is it something else? – makerofthings7 Sep 16 '12 at 14:35
See man kill, -9 is the signal to send. By default, kill sends a "soft" termination (letting the application/command handle the termination itself). This may not work if the application is stuck in some loop and never gets to handle the signal. -9 terminates on OS level. – patrix♦ Sep 16 '12 at 14:37
Would killall cat not work? – segiddins Oct 3 '12 at 14:41
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There might be several cats running through the (process) jungle, no reason to commit felinicide... – patrix♦ Oct 3 '12 at 14:50
@makerofthings7 In general, you should at least try kill -TERM or kill -INT (which is the same as ^C) first; jumping straight to SIGKILL is often a bad idea. – Blacklight Shining Nov 22 '12 at 1:11
up vote 1 down vote

Just tested this, type control-c in terminal, it should stop any running command.

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Perhaps the keyboard buffer was still full for me... ctrl c had no effect – makerofthings7 Sep 16 '12 at 4:05
Really! I tried several times, and each time I was able to get out of 'cat' no problem. – segiddins Sep 16 '12 at 4:06
I ended up going into activity monitor and killing the cat. Fortunately I only had to do it once – makerofthings7 Sep 16 '12 at 4:08
Fair enough. Seems like a strange thing to do, but I've seen (much) worse before. – segiddins Sep 16 '12 at 4:10
You might need to reset the terminal with command-R. – lhf Sep 16 '12 at 14:43

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