Tutorial 3 - Shell Programming

Tutorial 6

In this tutorial, we are going to familiarize ourselves with some sorting algorithms using shell programming. We will deal with bubble sort and insertion sort. We will also create some scripts ourselves as exercise. Use Vi, Emacs or Pico for editing the scripts. Login to one of the following Unix servers:

cs1.utdallas.edu

cs2.utdallas.edu

Use PuTTY or Xmanager for logging on as you learnt in Tutorial 1.

First example script: Bubble Sort

In our first example, we will write a script which will sort and print an array of integers or characters whose size is dynamically determined. Open your favorite Unix editor and type in the following script:

The bubble sort algorithm can be accessed through Bubble Sort.

Here is the script:

#!/bin/bash
# Bubble Sort

echo "Input unsorted numbers --"
read -a num

numlen=${#num[*]}

# Sort the array
x=$numlen
temp=0

# Standard algorithm for bubble sort
while [ $x -gt 0 ]; do
    i=0
    while [ $i -lt $[$numlen-1] ]; do
        j=$[$i+1]
        # If the previous element in the array is greater than the next then swap the

        # values.
        if [ ${num[i]} -gt ${num[j]} ]
        then
            temp=${num[i]}
            num[i]=${num[j]}
            num[j]=$temp
        fi
    i=$j
done
x=$[$x-1]
done

# Display the sorted array
echo "Sorted Output --"
echo ${num[*]}

Type the script in the editor and save the file as bubblesort.sh. Run it after assinging execute permission:

{cs1:~} chmod +x bubblesort.sh
{cs1:~} bubblesort.sh
Input unsorted numbers --
-1 10 200 -1 20 2 -100
Sorted Output --
-100 -1 -1 2 10 20 200

Second example script: Insertion Sort

In this example, we will write a script which will sort and print an array of integers or characters whose size is dynamically determined. Open your favorite Unix editor and type in the following script:

The insertion sort algorithm can be accessed through Insertion Sort.

Here is the script:

#!/bin/bash

echo "Enter numbers to be sorted"

read -a ARRAY

min=0

count=${#ARRAY[@]}

c=`expr $count - 1`

for ((i=0;$i<=$c;i++)) do

min=$i

index=${ARRAY[$i]}

for ((j=$i;$j<=$c;j++)) do

if [ ${ARRAY[$j]} -le $index ]

then

min=$j

index=${ARRAY[$j]}

done

ARRAY[$min]=${ARRAY[$i]}

ARRAY[$i]=$index

done

echo "=============================="

for ((i=0;$i<=$c;i++)) do

echo ${ARRAY[$i]}

done

echo "=============================="

Type the script in the editor and save the file as insertionsort.sh. Run it after assigning executes permission:

{cs1:~} chmod +x insertionsort.sh
{cs1:~} insertionsort.sh
Enter numbers to be sorted
-1 10 200 -1 20 2 -100

==============================
-100

-10

-1

200

==============================