use Fcntl qw (:DEFAULT :flock :seek);
my $file = '/dev/shm/tmpcount.txt';

for (1 .. 180) {
  print "$_\n";
  &filewrite($file,$_);
  sleep 1;
}

sub filewrite {							
  my ($file,$enc) = @_;
  open(my $fh,">", $file) || die "Can't open $file for reading: $!";
  my  $mode = LOCK_EX; 
  flock($fh,$mode) or die "Couldn't lock $file for write";
  print $fh $enc;
  close $fh;
}

##</code><code>##

use Fcntl qw (:DEFAULT :flock :seek);

my $file = '/dev/shm/tmpcount.txt';
my $c;

do {
  if (-e $file) {
    $c = &fileread($file);
    die "C is empty" unless ($c);
    print "count is $c \n";
  } else { print "File not found\n"; }
} until ($c == 180);

sub fileread {																				 # Read using perl IO 
my $file = shift;
open(my $fh, "<", $file) || die "Can't open $file for reading: $!";
my $mode = LOCK_SH;
flock($fh,$mode) or die "couldn't lock";
my $string = do { local $/; <$fh> };
close $fh;
return $string;
}