Re: Print line before match

In Perl, the key is to keep a copy of the previous line:

use strict;
use warnings;

my $prev;
while (<DATA>) {
    print $prev if $prev and /Northbound to/i or /Southbound to/i;
    $prev = $_;
}

__DATA__
interface POS2/1
 bandwidth 155520
 no ip address
 no ip directed-broadcast
 no ip proxy-arp
 load-interval 30
 shutdown
 crc 16
!
interface POS2/2
 description PL000000/00000000-O, NNI southbound To Somewhere fms 1111
+1111
 no ip address
 no ip directed-broadcast
 no ip proxy-arp
 encapsulation frame-relay IETF
 no ip mroute-cache
 crc 16
 frame-relay lmi-type cisco
!
interface POS2/2.30 point-to-point
 description POS2/2.30 fr dlci=30. By VPNSC: Job Id# = 9999
 ip vrf forwarding V1234:Customer
 ip address 192.168.254.2 255.255.255.252
 no ip directed-broadcast
 snmp trap link-status
 no cdp enable
 frame-relay interface-dlci 30 IETF
[download]

Prints:

interface POS2/2
[download]

Comment on Re: Print line before match Select or Download Code

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Re^2: Print line before match by ddrew78 (Beadle) on Mar 04, 2010 at 17:02 UTC
Perfect, works like a charm. Thank you so much.	[reply]
Re^2: Print line before match by ddrew78 (Beadle) on Mar 04, 2010 at 18:43 UTC
One more thing...now that I have this output (slightly modified) I need to go back thru a file and find all matches. Basically, I need to grab a line in one file, and find all lines in the second file that match, as well as several lines below. File 1: `interface POS2/2. interface POS4/1.` [download] File 2: interface POS2/1 bandwidth 155520 no ip address no ip directed-broadcast no ip proxy-arp load-interval 30 shutdown crc 16 ! interface POS2/2 description PL99999/9999999999-O, NNI southbound To Somewhere no ip address no ip directed-broadcast no ip proxy-arp encapsulation frame-relay IETF no ip mroute-cache crc 16 frame-relay lmi-type cisco ! interface POS2/2.30 point-to-point description POS2/2.30 fr dlci=30. By VPNSC: Job Id# = 111 ip vrf forwarding ABC:ABCD ip address 192.168.254.2 255.255.255.252 no ip directed-broadcast snmp trap link-status no cdp enable frame-relay interface-dlci 30 IETF ! interface POS2/2.31 point-to-point description POS2/2.31 fr dlci=31. By VPNSC: Job Id# = 112 ip vrf forwarding ACD:FGEI ip address 192.168.254.6 255.255.255.252 no ip directed-broadcast snmp trap link-status no cdp enable frame-relay interface-dlci 31 IETF ! [download] What I'm trying to extract from file 2, based on file 1 is this: interface POS2/2.30 point-to-point description POS2/2.30 fr dlci=30. By VPNSC: Job Id# = 111 ip vrf forwarding ABC:ABCD ip address 192.168.254.2 255.255.255.252 no ip directed-broadcast snmp trap link-status no cdp enable frame-relay interface-dlci 30 IETF interface POS2/2.31 point-to-point description POS2/2.31 fr dlci=31. By VPNSC: Job Id# = 112 ip vrf forwarding ACD:FGEI ip address 192.168.254.6 255.255.255.252 no ip directed-broadcast snmp trap link-status no cdp enable frame-relay interface-dlci 31 IETF [download] I have tried using the code below, but it doesn't work at all for me: `open(OUTFILE, ">outfile"); open(MYINPUTFILE, "file2"); open(MYINPUTFILE1, "file1"); while (<MYINPUTFILE>) { my($line) = $_; my $line1 = <MYINPUTFILE1>; chomp($line1); print OUTFILE if /$line1/ .. /frame-relay/; } close(MYINPUTFILE); close(MYINPUTFILE1);` [download] I will have to make more modifications after that, but I already have most of that written. Any help is always appreciated.	[reply] [d/l] [select]
Re^3: Print line before match by almut (Canon) on Mar 04, 2010 at 20:04 UTC
Problem is you're reading one line from file1 for every line in file2 (so you soon run out of lines in file1). I think you rather want nested loops, i.e. something along the lines of `open F1, "file1" or die $!; while (my $find = <F1>) { chomp $find; open F2, "file2" or die $!; while (<F2>) { print if /$find/ .. /frame-relay/; } }` [download] P.S. sorry about the first reply... (it didn't look like you wanted to learn Perl).	[reply] [d/l]
Re^4: Print line before match by ddrew78 (Beadle) on Mar 04, 2010 at 20:27 UTC
Great, works like a charm. Exactly what I was looking for.	[reply]