Page MenuHomeFreeBSD

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

Authored by lidl on Mar 4 2019, 2:44 PM.
Tags
None
Referenced Files
Unknown Object (File)
Jan 23 2024, 9:41 AM
Unknown Object (File)
Dec 23 2023, 4:13 PM
Unknown Object (File)
Dec 23 2023, 2:17 AM
Unknown Object (File)
Nov 8 2023, 5:09 AM
Unknown Object (File)
Oct 7 2023, 3:59 AM
Unknown Object (File)
Sep 12 2023, 12:18 PM
Unknown Object (File)
Aug 26 2023, 2:52 PM
Unknown Object (File)
Aug 9 2023, 5:51 AM

Details

Summary

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}'

and

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

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

Diff Detail

Repository
rS FreeBSD src repository - subversion
Lint
Lint Not Applicable
Unit
Tests Not Applicable