Re: get n lines before or after a pattern

[xiaoyafeng]

try natatime in List::MoreUtils, maybe it makes your code more elegant? ;)

use List::MoreUtils qw/natatime/;
my @contents = <DATA>;

pop @contents;
shift @contents;
my $it = natatime 8, @contents;
    while (my @vals = $it->())
    {
        print "@vals[0,1,2] \n" if $vals[2] =~ /jack/;
    }
  

__DATA__
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

The another advantage of this approach compared to other way is you won't lose the rest part of every chunk. you can print any elements of @vals by changing slice.

[Kenosis]

Nice use of List::MoreUtils qw/natatime/! However, consider using /\bjack\b/, as your current regex also matches "jackson", "jackie", "jacklyn", etc.

[ww]

Nice (and + +), but the regex can go astray:

C:>perl -E "my $word="jackhammer"; if ($word =~ /\bjack\b/) {
    say $word;
} else {
    say \"No word-boundry-delimited 'jack's' found in $word\";
}"

No word-boundry-delimited 'jack's' found in jackhammer

[Kenosis]

Perhaps I'm missing something, but I wouldn't want to find "jackhammer" if I were searching for "jack" as the first name--as listed in the OP's data set. However, the non-word-boundary regex is perfect for finding all first names containing the sub-string "jack", as $vals[2] =~ /jack/ would.

[ww]

Flip that coin. It's not a question of searching for "jackhammer." It's a matter of what *jack* elements could be present in the data (whose contents are, at least possibly, unknown at the time you start writing the code)... as, for example, jackson (mississippi) or jackson hole, colorado.

But note: my reply is directed, not to you, but to the parent of your node... and, thus, casts no aspersions on your prior remark; in fact, it appears to say pretty much the same thing, but you said it first