UNIX for Dummies Questions & Answers

#!/usr/bin/perl 
$var=reverse ("AAAACCCTGGATTTCCCCAATTTTTTTTTTTTT");
while($v=chop($var)) {  print $v if($v ne $prev); $prev=$v; }

#!/bin/ksh

echo "Enter your string containing poly character :"
read input_string

prev_char=`echo $input_string | cut -c1`

string_length=`echo $input_string | wc -c`

i=1
monostring=$prev_char

while [ $i -le $string_length ]
do
curr_char=`echo $input_string | cut -c$i`
if [ "$curr_char" != "$prev_char" ]
then
    monostring=`echo ${monostring}${curr_char}`
fi
prev_char=$curr_char
i=$(($i+1))
done

echo "\nThe mono character output is :\n $monostring"

$ echo AAAACCCTGGATTTCCCCAATTTTTTTTTTTTT | tr -s [A-Z]
ACTGATCAT

$ echo AAAACCCTGGATTTCCCCAATTTTTTTTTTTTT | sed "s/\(.\)\1\{1,\}/\1/g"
ACTGATCAT