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Every couple of months I return to a gnu screen session just to find out that the running script was stalling for hours or days. My suspicion is, that I, while I try to detach, accidentally press some key combination that makes the process halt. When I attach later and notice the stalling I often see that my tries to detach have left command line input like D^[[D^[[D or ^[[. But I was not able reproduce it. Do you have an idea?

I experienced this behaviour with python scripts and C++ code.

Framester
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    ^[[D is the character string typically created by pressing the "left cursor" key. Pauses are likely to happen if you press control-S by mistake when aiming for control-A. – Stephen Harris Aug 23 '16 at 14:39
  • Wow, thanks! Here a link I found searching for control-s http://unix.stackexchange.com/questions/12107/how-to-unfreeze-after-accidentally-pressing-ctrl-s-in-a-terminal @stehpen, can you create an answer so I can accept it? – Framester Aug 23 '16 at 14:44

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The ^[[D is a key sequence normally created by pressing the cursor left key. This indicates you hit this key by mistake before detaching the session.

Screen pauses may be caused by pressing Control+S keys. This is using Xon/Xoff flow control. It can be restarted with Control+Q. Since the S key is next to the A key it's possible you hit this by mistake when detaching the session.

Stephen Harris
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As Stephen answered, it's likely that the script is stopped because you've hit XOFF or ^S by accident.

Apart from not hitting it, you can disable software flow control by running stty -ixon in that terminal. (I seem to have that in my .bash_profile, I think it's because I've stopped my IRC client too often with it.)

ilkkachu
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