Shell Programming and Scripting

nawk 'BEGIN {FS=RS;RS="!"} /interface loopback0/
{for(i=1;i<=NF; i++) if ($i ~ /ip address/){split($i,a, OFS "|/");print a[3]}}' <file>

my $loopback = "interface loopback0 ";
 
foreach my $host (@HOST){
my $out_fh = "$CONFIG_DIR/$host";
open (FILE, "<$out_fh") or die "Can't open $out_fh";
my @lines = <FILE>;
my $lines; my $i;
for $i(0..$#lines) {
next unless $lines[$i] =~ /$loopback/;
my $a = $i + 2 < 0 ? 0 : $i + 2;;
for $i($a) {
if ($lines[$i] =~ /ip address/) {
my ($out) = (split / /, $lines[$i])[4];
$out = (split /\//, $out)[0];
print "$out\n";
}
}
}
}
close (FILE);

!
interface loopback0 loopback
description My Router Loopback
ip address 10.30.160.10/32 tag 200
ip source-address tftp ftp 
!
interface loopback1 loopback
description External BGP
ip address 10.159.192.9/32 tag 201
!
interface loopback2 loopback
ip address 10.159.168.33/32 tag 202
ip source-address radius 
!
interface loopback3 loopback
description ID: Management;
ip address 10.81.114.6/32 tag 203
ip source-address snmp syslog 
!

NAME
       a2p - Awk to Perl translator

SYNOPSIS
       a2p [options] [filename]

DESCRIPTION
       A2p takes an awk script specified on the command line (or from standard
       input) and produces a comparable perl script on the standard output.

$ echo nawk 'BEGIN {FS=RS;RS="!"} /interface loopback0/{for(i=1;i<=NF; i++) if ($i ~ /ip address/){split($i,a, OFS "|/");print a[3]}}' | a2p
#!/usr/bin/perl
eval 'exec /usr/bin/perl -S $0 ${1+"$@"}'
    if $running_under_some_shell;
			# this emulates #! processing on NIH machines.
			# (remove #! line above if indigestible)

eval '$'.$1.'$2;' while $ARGV[0] =~ /^([A-Za-z_0-9]+=)(.*)/ && shift;
			# process any FOO=bar switches

$[ = 1;			# set array base to 1
$FS = ' ';		# set field separator
$, = ' ';		# set output field separator
$\ = "\n";		# set output record separator

$FS = $/;
$/ = '!';

whle (<>) {
     chomp;	# strip record separator
    @Fld = split($FS, $_, -1);
    print $_ if $nawk;if (/interface loopback0/) {
	for ($i = 1; $i <= $#Fld; $i++) {
	    if ($Fld[$i] =~ /ip address/) {
		@a = split($, . '|/', $Fld[$i], -1);
		print $a[3];
	    }
	}
    }
}

foreach my $host (@HOST){
my $out_fh = "$CONFIG_DIR/$host";
open (FILE, "<$out_fh") or die "Can't open $out_fh";
     my @lines = <FILE>;
     my $lines; my $i;
     for $i(0..$#lines) {
        next unless $lines[$i] =~ /$loopback/;
           my $a = $i + 1 < 0 ? 0 : $i + 1;;
           my $b = $i + 2 < 0 ? 0 : $i + 2;;
             for $i($a) {
                if ($lines[$i] =~ /ip address/) {
                   my ($out) = (split / /, $lines[$i])[4];
                   $out = (split /\//, $out)[0];
                   print "$out\n";
                }
              }
             for $i($b) {
                if ($lines[$i] =~ /ip address/) {
                   my ($out) = (split / /, $lines[$i])[4];
                   $out = (split /\//, $out)[0];
                   print "$out\n";
                }
              }
      }
close (FILE);
}