I need to run a certain command (ngrok in this case) for a few seconds, capture all the output, filter out some variables and then detach the process, making it run invisibly in the background. How can I do that?
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capture the output where? In a file, shell variable?– Stéphane ChazelasJul 29, 2017 at 17:34
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file, variable, doesn't matter– freemanovecJul 29, 2017 at 17:35
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1 Answer
(cmd &) | (timeout --foreground 2 cat; cat > /dev/null &)
Would show you the output of cmd for 2 seconds and then return, with cmd running in background with its output going to /dev/null.
You can redirect that to a file or store in a variable with:
var=$(that command)
answered Jul 29, 2017 at 17:42
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ngrok output can't unfortunately get captured like this, because it's sort of like apt output line updating, which doesn't get captured in a file. So this solution doesn't output anything. Thanks anyway! Jul 29, 2017 at 18:09
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I was able to make it work using this solution when I disabled the buffering via the expect's unbuffer. Thanks! Jul 29, 2017 at 18:15
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@freemanovec, you may try to use
stdbuf -o0beforeunbufferif available asunbufferhas a few issues. Jul 29, 2017 at 18:36