Re^2: get n lines before or after a pattern

[johngg]

Reading "records" rather than lines is a nice approach. One minor point, your local is not really local as you have not confined it to a particular scope so it applies from the point it appears until the end of the script.

Rather than the split and array slice, another approach could be to open a file handle against a reference to the record so that you can read it line by line in an inner scope and just print the lines you want. This has the advantage that the record layout can change and it will still work.

use strict;
use warnings;

open my $inFH, q{<}, \ <<EOD or die $!;
start
id 10 
address Richmond 
name jack 
xxxxx
aaaaa
lastname black 
yyyy
zzzzz
id 11
address Central
name rick 
cccccc
dddddd
lastname hanna
eeeee
yyyyy
id 12
address denver 
name jack
sssss
tttttt
lastname strong
rrrrr
mmmmm
id 13
address Virginia 
name mick 
aaaaaaa
ooooooo
lastname jagger
gggggg
hhhhhh
id 14 
address Maine
name rick
sssss
sssss
lastname stewart
ssssss
ffffff
end
EOD

{
    local $/ = q{id};
    while ( my $record = <$inFH> )
    {
        next unless $record =~ m{name\s+jack\b};
        chomp $record;
        $record = $/ . $record;
        {      
            local $/ = qq{\n};
            print for do {
               open my $recordFH, q{<}, \ $record or die $!;
               grep { m{^(?:id|address|name|lastname)} }
               <$recordFH>;
               };
        }
    }
}

I hope this is of interest.

[Kenosis]

This is of interest, and excellent, too, JohnGG!

I was aware that I didn't confine the local $/; to a block, not thinking too much about the code snippet. However, I'll remember--as a best practice--to do so with future local (dynamically scoped) variables. It was good to point this out.

I like your refined/seasoned coding: scoping, reading in a multi-line record, opening a file handle on the record-containing scalar, and then grepping through the lines to display the OP's desired output.

Indeed, this is of interest, very well thought out, and very much appreciated.

Thank you.