Array Basics Shell Scripting | Set 2 (Using Loops)

It is recommended to go through Array Basics Shell Scripting | Set-1 Introduction Suppose you want to repeat a particular task so many times then it is a better to use loops. Mostly all languages provides the concept of loops. In Bourne Shell there are two types of loops i.e for loop and while loop. To Print the Static Array in Bash 1. By Using while-loop ${#arr[@]} is used to find the size of Array. 

bash

# !/bin/bash
# To declare static Array
arr=(1 12 31 4 5)
i=0

# Loop upto size of array
# starting from index, i=0
while [ $i -lt ${#arr[@]} ]
do
    # To print index, ith
    # element
    echo ${arr[$i]}

    # Increment the i = i + 1
    i=`expr $i + 1`
done

Output:

1
2
3
4
5

Time Complexity: O(n)
Auxiliary Space: O(1)

2. By Using for-loop 

bash

# !/bin/bash
# To declare static Array
arr=(1 2 3 4 5)

# loops iterate through a
# set of values until the
# list (arr) is exhausted
for i in "${arr[@]}"
do
    # access each element
    # as $i
    echo $i
done

Output:

1
2
3
4
5

Time Complexity: O(n)
Auxiliary Space: O(1)

To Read the array elements at run time and then Print the Array. 1. Using While-loop 

bash

# !/bin/bash
# To input array at run
# time by using while-loop

# echo -n is used to print
# message without new line
echo -n "Enter the Total numbers :"
read n
echo "Enter numbers :"
i=0

# Read upto the size of
# given array starting from
# index, i=0
while [ $i -lt $n ]
do
    # To input from user
    read a[$i]

    # Increment the i = i + 1
    i=`expr $i + 1`
done

# To print array values
# starting from index, i=0
echo "Output :"
i=0

while [ $i -lt $n ]
do
    echo ${a[$i]}

    # To increment index
    # by 1, i=i+1
    i=`expr $i + 1`
done

Output:

Enter the Total numbers :3
Enter numbers :
1
3
5
Output :
1
3
5

Time Complexity: O(n)
Auxiliary Space: O(1)

2. Using for-loop 

bash

# !/bin/bash
# To input array at run
# time by using for-loop

echo -n "Enter the Total numbers :"
read n
echo "Enter numbers:"
i=0

# Read upto the size of
# given array starting
# from index, i=0
while [ $i -lt $n ]
do
    # To input from user
    read a[$i]

    # To increment index
    # by 1, i=i+1
    i=`expr $i + 1`
done

# Print the array starting
# from index, i=0
echo "Output :"

for i in "${a[@]}"
do
    # access each element as $i
    echo $i
done

Output:

Enter the Total numbers :3
Enter numbers :
1
3
5
Output :
1
3
5

Time Complexity: O(n)
Auxiliary Space: O(1)