@frostschutz: Hopefully made that slightly clearer in the help message, and added a -k, --cls flag that *will* always abort early

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Obviously, in your example, unless there's a significant delay between the two calls during a single iteration, what'll happen is that the controller will bundle the two refreshes together, and you'll probably almost never see the line on screen

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Without knowing more context about your use-cases, what would make more sense to me would be a single
fbink -c "$line" (i.e., clear the screen, then print $line)

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