Bubble Sort Shell Script

#!/bin/bash
# SCRIPT: bubblesort.sh
# LOGIC:
# Bubble sort is a simple sorting, it works by repeatedly stepping
# through the list to be sorted, comparing two items at a time and
# swapping them if they are in the wrong order. If you are sorting
# the data in Ascending order, at the end of the first pass, the
# "heaviest" element has move to bottom. In the second pass, the
# comparisons are made till the last but one position and now second
# largest element is placed at the last but one position. And so
# forth.
#
#####################################################################
#                      Define Functions Here                        #
#####################################################################

printnumbers()
{
echo ${ARRAY[*]}

#You can also use bellow code
#for ((i=0;i<count;i++))
#do
#echo -n " ${ARRAY[i]} "
#done
}

exchange()
{
temp=${ARRAY[$1]}

ARRAY[$1]=${ARRAY[$2]}

ARRAY[$2]=$temp

}

sortnumbers()
{
for (( last=count-1;last>0;last--))
do
    for((i=0;i<last;i++))
    do
      j=$((i+1))
      if [ ${ARRAY[i]} -gt ${ARRAY[j]} ]
      then

       exchange $i $j

      fi
    done
done
}

#####################################################################
#                       Variable Initialization                     #
#####################################################################

echo "Enter Numbers to be Sorted"

read -a ARRAY

count=${#ARRAY[@]}

#####################################################################
#                       Main Script Starts Here                     #
#####################################################################

echo "--------------------------------------------------------------"

echo "Numbers Before Sort:"

printnumbers

echo

sortnumbers

echo "Numbers After Sort: "

printnumbers

echo "--------------------------------------------------------------"



OUTPUT:

[root@www blog]# sh bubblesort.sh
Enter Numbers to be Sorted :
78 34 12 98 21 8 36 98 12 88 7 5 61 -12 62 -1 77 -46
------------------------------------------------------
Numbers Before Sort:
78 34 12 98 21 8 36 98 12 88 7 5 61 -12 62 -1 77 -46

Numbers After Sort:
-46 -12 -1 5 7 8 12 12 21 34 36 61 62 77 78 88 98 98
------------------------------------------------------

NOTE: If we complement the if condition in this program, it will give
out the sorted array in descending order.

Method2: Without Using Arrays
#!/bin/bash
# SCRIPT: bubblesort2.sh
# Without using arrays
#
#####################################################################
#                       Define Functions Here                       #
#####################################################################

printnumbers()
{
k=1
while [ $k -le $max ]
do
eval echo -n "\$x$k"
echo -n " "
let k++
done
echo
}

#####################################################################
#                        Variable Initialization                    #
#####################################################################

echo -n "Enter Total Numbers to be Sorted : "
read max
count=1
while [ $count -le $max ]
do
echo -n "Enter number $count: "
read x$count
let count++
done

#####################################################################
#                       Main Script Starts Here                     #
#####################################################################

echo -e "\nElements Before Sort"
printnumbers

for (( last=count-1;last>0;last--))
do
  for ((i=1;i<last;i++))
  do
     j=$((i+1))
     eval sval=\$x$i
     eval nval=\$x$j

#The eval command evaluates the command line to complete any shell
#substitutions necessary and then executes the command. So $i and $j
#substituted first then $x1 and $x2 evaluated.

     if [ $sval -gt $nval ]
     then
     eval x$i=$nval
     eval x$j=$sval
     fi
   done
done

echo  "Elements After Sort: "
printnumbers



OUTPUT:

[root@www shell]# sh bubblesort2.sh
Enter Total Numbers to be Sorted : 6
Enter number 1: 12
Enter number 2: -4
Enter number 3: 6
Enter number 4: -11
Enter number 5: 43
Enter number 6: 9

Elements Before Sort
12 -4 6 -11 43 9
Elements After Sort:
-11 -4 6 9 12 43