ddrew78 has asked for the wisdom of the Perl Monks concerning the following question:

This is turning into a rather strange issue. Whenever I try to execute this command:
grep -B 1 -i "Northbound to" file1 > file2
grep -B 1 -i "Southbound to" file1 >> file2

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I get an error saying 
grep: illegal option -- B
Usage: grep -hblcnsviw pattern file . . .
grep: illegal option -- B
Usage: grep -hblcnsviw pattern file . . .

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Is there another way of displaying one line before either or both matches? Obviously what I'm looking for is the interface that this is on. Below is a small portion of 'file1'. Thanks for any and all ideas. 
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]

Replies are listed 'Best First'.
Re: Print line before match
by toolic (Bishop) on Mar 04, 2010 at 14:57 UTC
    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]
[reply]
[d/l]
[select]
      Perfect, works like a charm. Thank you so much.
[reply]
      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]

        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: Print line before match
by almut (Canon) on Mar 04, 2010 at 14:48 UTC

    Maybe you should get a grep which supports the -B option... GNU grep does, and should compile on nearly any platform.

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[d/l]
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