The while(true) is not a problem because the loop contains sleep 0.5 which relinquishes half a second of CPU time in each of the loop's iterations. Because of that (and the lightweightness of the xsel command invocation which comprises the other part of the loop), the CPU resources taken up by the loop will be exceedingly tiny even on the slowest of Ubuntu machines.

Just to provide some context on the extent of the issue. Running the spec suite for Discourse results in 2,698,774 rows being printed to STDERR.