Shell Programming and Scripting

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#!/bin/ksh
IAm=${0##*/}
TSF="$HOME/.LastTimeStamp"

if [ ! -f $TSF ]
then	printf '%s: Time stamp file (%s) not found.\n\tProcessing all timestamps.\n' \
	    "$IAm" "$TSF" >&2
	ts=0
else	read ts < "$TSF"
fi
awk -v TS="$ts" -v TSF="$TSF" '
$1 + 0 <= TS {
	# Skip previous processed timestamps.
	next
}
{	# Do what every you want to do with the new timestamp...
	# Save last completed time stamp.
	print $1 > TSF
	close(TSF)
}' input_file...

#!/usr/bin/perl
open (FH,"/path/to/file.txt") or die "cannot open file \n";
my $pos=0;
while (1) {
  seek(FH,$pos,0);
  while (<FH>) {
    print $_;
  }
  $pos=tell(FH);
}

#!/bin/bash
f=0
while [ ${f} -eq 0 ] ; do
    for i in {1..70} ; do
        read a || { f=1 ; break ; }
        echo "${a}"
    done
done < <(tac yourfile.txt)