http://www.perlmonks.org?node_id=1051866


in reply to perl one line for advanced grep (current line and next one)

How long can the line be?

There's no perlrun switch that makes this easy, but regular old IF-ELSIF and a state variable will get the job done.

perl -ne 'if (/PAT/) { print; $aft = 1 } elsif ($aft) { print "$_---\n"; $aft = 0; }' FILENAME

No doubt this could be golf'd into submission, but left reasonably verbose here for clarity.

The bigger question (to me) is, "why?" My system grep implements Perl regular expressions, plus there have been multiple Perl grep implementations such as grepp -- Perl version of grep. There is a point at which the convenience of a one-liner can't make up for the power of a purpose-built utility. Maybe this isn't that point, but it'd be getting awfully close, for me.

use strict; use warnings; omitted for brevity.

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Re^2: perl one line for advanced grep (current line and next one)
by Anonymous Monk on Sep 02, 2013 at 16:58 UTC
    I'll golf it readable (untested): 
    perl -ne '
    print, $aft++, next if /PAT/;
    $aft or next;
    print "$_---\n";
    $aft = 0;'

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