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Remove an unneeded 'tail -n 1' from a pipeline

Authored by lidl on Mar 4 2019, 2:44 PM.



When piping to awk, it's almost always an anti-pattern to use 'grep' first.

When not in a pipeline, sometimes it is faster to use tail, as awk must process all the lines, and won't 'seek'. In a pipeline, both must process all lines, so we might as well skip the extra process creation and just use awk for all the processing.

Test Plan

Verify that the output between:

zpool list -v $rootdev | tail -n 1 | awk '{print $1}'


zpool list -v $rootdev | awk 'END {print $1}'

Are the same on all my systems. The output is the same.

Diff Detail

rS FreeBSD src repository
Automatic diff as part of commit; lint not applicable.
Automatic diff as part of commit; unit tests not applicable.

Event Timeline

lidl created this revision.Mar 4 2019, 2:44 PM
jilles accepted this revision.Mar 8 2019, 10:00 PM
This revision is now accepted and ready to land.Mar 8 2019, 10:00 PM
This revision was automatically updated to reflect the committed changes.