Re: get n lines before or after a pattern

Here's another option:

use Modern::Perl;

my $searchFor = 'jack';
local $/ = 'id ';

while (<DATA>) {
    next if !/\nname\s+\b$searchFor\b/;
    say 'id ', join "\n", ( split "\n" )[ 0, 1, 2, 5 ];
}

__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
[download]

Output:

id 10 
address Richmond 
name jack 
lastname black 
id 12
address denver 
name jack
lastname strong
[download]

Hope this helps!

Comment on Re: get n lines before or after a pattern Select or Download Code

Replies are listed 'Best First'.
Re^2: get n lines before or after a pattern by johngg (Canon) on Jul 25, 2012 at 23:54 UTC
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. Read more... (1110 Bytes) I hope this is of interest. Cheers, JohnGG	[reply] [d/l]
Re^3: get n lines before or after a pattern by Kenosis (Priest) on Jul 26, 2012 at 03:41 UTC
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 `grep`ping 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.	[reply] [d/l] [select]