Shell Programming and Scripting

#! /opt/third-party/bin/perl

my($i, %fileHash_a, %fileHash_b);

for( ;1; sleep 5 ) {

%fileHash_a = ();
%fileHash_b = ();

open(FILE, "< a") || die "file a <$!>\n";

while( <FILE> ) {
  chomp;
  $fileHash_a{$_} = $i++;
}

close(FILE);

$i=0;
open(FILE, "< b") || die "file b <$!>\n";
while( <FILE> ) {
  chomp;
  $fileHash_b{$_} = $i++;
}

close(FILE);

  open(FILE, "> update") || die "update <$!>\n";

  foreach my $k ( keys %fileHash_a ) {
    if ( exists $fileHash_b{$k} ) {
    }
    else {
      print FILE $k . "\n";
    }
  }
  close(FILE);
}


exit 0

$cat tmp1
234
678
345
$cat tmp2
345
678

$sort tmp1 > tmp1.sort
$sort tmp2 > tmp2.sort
$comm -23 tmp1.sort tmp2.sort
234

$grep -v -f tmp2 tmp1
234