also sprach Martin McCormick <martin@dc.cis.okstate.edu> [2005.02.11.1846 +0100]:
> sed is one of my favorite UNIX applications and I see examples
> of expressions that I have read about but hadn't tried so this is a
> good learning experience. The -ne tells sed to quietly use the next field
> which is the part in single quotes as a regular expression
> 's,[:space:]install$,,p'
>
> Here's where I think a switch is in the opposite position so
> to speak. This produces a perfect list of every deinstalled package
> on the system, some white space and then a single d.
man, this is not my day. use [[:space:]] instead of [:space:].
> The part of the sed expression I am not familiar with is the
> very last part of the quoted block that says
> $,,p The white space before the word install is the trigger.
it's basically a grep and sed combined: replace "[[:space:]]install"
at the end of the line with nothing and only print (-n inhibits
automatic printing) lines where the replacement took place.
you could also do it with grep and awk:
grep '[[:space:]]install$' | awk '{print$1}'
but why spawn two processes when one suffices?
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.''`. martin f. krafft <madduck@debian.org>
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