100 Shell Script Examples [Free Downloads]

Q: What is $1 shell script?

In a shell script, $1 refers to the first command-line argument passed to the script when executed. It allows the script to access and use the value of the first argument provided by the user.

Q: What is the popular shell script?

One of the popular and widely used shell scripts is the Bash shell script. Bash (Bourne Again SHell) is the default shell for most Unix-like operating systems, including Linux. Many scripts are written in Bash due to its versatility and widespread adoption. It is commonly used for automating tasks, managing system configurations, and creating custom utilities on Unix-based systems.

Q: Which shell is best for scripting?

Bash (Bourne Again Shell) is widely considered one of the best shells for scripting, offering a balance of features, compatibility, and widespread use on Unix-like systems, including Linux.

A shell script in Linux is a text file containing a sequence of commands written in a scripting language interpreted by the shell. The shell acts as an interface between the user and the operating system, interpreting commands entered by the user or read from a script file. The GNU Bourne-Again Shell also known as bash is the default shell for most of the Linux distributions. It commonly runs in its interactive form which is the Command Line Interface (CLI).

In this article, you will find 100 shell script examples along with a basic understanding of Shell Scripting.

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Bash Shell Script Examples

Shell scripts are primarily written in scripting languages like Bash (Bourne Again SHell), sh (Bourne Shell), C Shell, Korn Shell (ksh), and others. Among these, Bash is the default shell for most Linux distributions. The very first line of a bash script needs to start with the SheBang (#!) followed by the path to the bash executable program (/bin/bash). Here are 100 examples of basic shell scripts:

1. Defining Variables in a Bash Script

Variables in shell scripting are containers for storing necessary information. In Bash Script, declare a variable by assigning a value to its reference by = operator. Furthermore, print the assigned values using echo $(VARIABLE_NAME).

The syntax for Variables in Shell Scripting is given below:

VARIABLE_NAME=VALUE

The rules for Variables in Shell Scripting are as follows:

Use the equal sign (=) to assign values to variable names.
Variable names are case sensitive i.e. ‘A’ and ‘a’ are different.
To refer to a variable use the dollar sign ($) e. $VARIABLE_NAME.
While updating/changing the variable values use only the variable name with the assignment operator(=) i.e. VARIABLE_NAME= NEW_VALUE.
No need to define variable type while declaring variables.
Enclose multiple words or string values within Single Quote (‘ ‘) to consider all characters as input.

Here is an example script for defining variable:

#!/bin/bash
# Declaration of variables
name=Tom
age=12
# Displaying variables
echo $name $age

Output:

Tom 12

2. Display User Input

You can take user input with the read command and store it in a variable. Next, use echo $(VARIABLE_NAME) to print the user input. Here’s how:

#!/bin/bash
read num
echo “The number is: $num”

3. Read User Input With Prompt Message

The read command used with option -p allows you to prompt a message along with taking user input. You can use echo $(VARIABLE_NAME) to display the user input on the screen. Here’s an example:

#!/bin/bash

read -p "Enter a number:" num
echo “The number is: $num”

Output:

Enter a number: 12
The number is: 12

4. Concatenating Multiple Variables

To concatenate multiple variables and store them into a single variable, enclose them with a double quotation (“ ”) and then write the variables within {} consecutively. Here is an example:

#!/bin/bash

# Declaration of variables
name='My name is Tom.'
age='My age is 12.'

# Concatenation
info="${name} ${age}"
echo "Result: $info"

Output:

Result: My name is Tom. My age is 12.

5. Passing Values to Variables as Command Line Arguments

For passing values as command line arguments, you have to run the script along the values in a sequence. Later access these values using the $ and input sequence number. Here’s how:

#!/bin/bash
name=$1
age=$2
echo "My name is $name. My age is $age."

Run the script using:

bash var_example5.sh Tom 12

Output:

My name is Tom. My age is 12.

6. Print Environment Variable Using Bash Script

You can store an Environment Variable like other variables and print it using ${!..} syntax. The example script below shows how:

#!/bin/bash
read -p "Enter an Environment Variable name:" var
echo "Environment:${!var}"

Output:

Enter an Environment Variable name:
HOME
Environment:/home/anonnya

7. Adding Two Numbers

Run an addition operation using the + operator between defined variables and enclose them with $(). Here’s an example:

#!/bin/bash

num1=10
num2=20
sum=$(($num1+$num2))
echo "The Sum is: $sum"

Output:

The Sum is: 30

8. Subtracting Two Numbers

Subtract two numbers using the - operator between defined variables and enclose them with $(). Here’s an example:

#!/bin/bash

num1=30
num2=20
dif=$(($num1-$num2))

echo "The difference is: $dif"

Output:

The difference is: 10

9. Division of Two Numbers

Run a division using the / operator between defined variables and enclose them with $(). Here’s an example script:

#!/bin/bash

num1=30
num2=5
div=$(($num1/$num2))

echo "The division is: $div

Output:

The division is: 6

10. Calculating the Remainder of a Division

For generating the remainder of a division use the % operator between defined variables and enclose them with $(). Here’s an example script:

#!/bin/bash

num1=30
num2=20
mod=$(($num1%$num2))

echo "The remainder is: $mod"

Output:

The remainder is: 10

11. Generate a Random Number Using Bash Script

To generate a random number in bash, use the RANDOM function enclosed with $(). For example:

#!/bin/bash

echo $((RANDOM))

12. Generating a Random Number Between Two Given Numbers

To generate a random number in bash, use the RANDOM function with the lower and upper bound in the syntax (lower + RANDOM % upper) or ($RANDOM % ($upper - $lower + 1) + $lower ). Use read command to take the upper and lower values from the user. Here’s a complete script:

#!/bin/bash

read -p "Enter minimum range:" min
read -p "Enter maximum range:" max

r_num=$(( $RANDOM % ($max - $min + 1) + $min ))
echo "Random Number: $r_num"

Output:

Enter minimum range:10
Enter maximum range:35
Random Number: 24

13. Performing Mathematical Operations Without Storing

To perform multiple mathematical operations without storing them in a separate variable, write the operations inside echo . This is how:

#!/bin/bash

read -p "Enter a number:" num1
read -p "Enter a smaller number:" num2

echo "Addition: $(($num1 + $num2))"
echo "Subtraction: $(($num1 - $num2))"
echo "Multiplication: $(($num1 * $num2))"
echo "Division: $(($num1 / $num2))"

Output:

Enter a number:35
Enter a smaller number:15
Addition: 50
Subtraction: 20
Multiplication: 525
Division: 2

14. Performs a Bitwise Operation Based on User Input

The given script performs either of the bitwise AND, OR, NOT operations by &, |, ! respectively on the 2 input numbers. If the user enters any other operand as input then the script displays an error message.

#!/bin/bash

read -p "Enter two numbers: " num1 num2
read -p "Enter operation to perform (AND, OR, NOT): " op

case $op in

AND) echo "Result: $num1 & $num2 = $((num1&num2))";;
OR) echo "Result: $num1 | $num2 = $((num1|num2))";;
NOT) echo "Result: $num1 ^ $num2 = $((num1^num2))";;
*) echo "Invalid operator.";;

esac

Output:

Enter two numbers: 4 5
Enter operation to perform (AND, OR, NOT): AND
Result: 4 & 5 = 4

15. Check If a Number is an Even or Odd

If a number is even, then its remainder after dividing by 2 will be 0. Otherwise, the number is odd. So, use the remainder operator % within if-else to check if a number is even or odd. Here’s how:

#!/bin/bash

read -p "Enter a number:" num
if [ $((num%2)) == 0 ]
then
echo "The number is even"
else
echo "The number is odd"
fi

Output:

Enter a number:25
The number is odd

16. Perform an Arithmetic Operation Based on User Input

To perform user input-based operations implement the if-elif-else condition like the below script:

!/bin/bash

read -p "Enter a number:" num1
read -p "Enter a smaller number:" num2
read -p "Enter an operand:" op

if [ $op == + ]
then
echo "$num1 + $num2 = $((num1+num2))"
elif [ $o == - ]
then
echo "$num1 - $num2 = $((num1-num2))"
elif [ $op == * ]
then
echo "$num1 * $num2 = $((num1*num2))"
elif [ $op == / ]
then
echo "$num1 / $num2 = $((num1/num2))"
else
echo "Operator not listed"
fi

Output:

Enter a number:34
Enter a smaller number:14
Enter an operand:+
34 + 14 = 48

17. Performs a Logical Operation Based on User Input

You can perform user-input based operations with the case statement as the below script:

#!/bin/bash

read -p "Enter two values: "  val1 val2
read -p "Enter an operation(and/or/not) to perform:" op

case $op in
and)
if [[ $val1 == true && $val2 == true ]]
then
echo "Result: true"
else
echo "Result: false"
fi;;
or)
if [[ $val1 == true || $val2 == true ]]
then
echo "Result: true"
else
echo "Result: false"
fi;;
not)
if [[ $val1 == true ]]
then
echo "Result: false"
else
echo "Result: true"
fi;;
*) echo "Invalid operator."
esac

Output:

Enter two values: true false
Enter an operation(and/or/not) to perform:or
Result: true

18. Check If a Given Input is a Valid Email ID

A valid email can be checked by defining the email syntax ^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$ inside the if condition. The below script shows how:

#!/bin/bash

read -p "Enter an email ID: " id
if [[ $id =~ ^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$ ]]
then
echo "This is a valid email ID!"
else
echo "This is not a valid email ID!"
fi

Output:

Enter an email ID: [email protected]
This is a valid email ID!

19. Check If a Given Input is a Valid URL

To check a valid URL, use a simple if-else condition with the URL pattern ^(http|https)://[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$. The below script shows how:

#!/bin/bash

read -p "Enter a URL: " url
if [[ $url =~ ^(http|https)://[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$ ]]
then
echo " This is a valid URL!"
else
echo "This is not a valid URL!"
fi

Output:

Enter a URL: abcdefg1234
This is not a valid URL!

20. Check if a Given Number is Positive or Negative

To check if a given number is positive or negative, use the comparison operators (-gt, -lt) inside the if-elif-else block.

#!/bin/bash
read -p "Enter a number:" num
if [ $num -gt 0 ]
then
echo "The number is Positive!"
elif [ $num -lt 0 ]
then
echo "The number is Negative!"
else
echo "The number is Zero!!"
fi

Output:

Enter a number:12
The number is Positive!

21. Check If a File is Writable

To check if a file is writable, use -w option with the variable that stores the filename inside a if block. For example, if fname is the variable that stores the filename to check, use -w $fname inside if block to check if it is writable. Here’s how:

#!/bin/bash
read -p "Enter a File Name:" fname
if [ -w $fname ]
then
echo "The File $fname is writable."
else
echo "The File $fname is not writable."
fi

Output:

Enter a File Name:file1.txt
The File file1.txt is writable.

22. Check If a File Exists or Not

To check if a file exists, use -f option with the variable that stores the filename inside a if block. For example, if fname is the variable that stores the filename to check, use -f $fname inside if block to check if it exists. Here’s how:

#!/bin/bash
read -p "Enter a File Name:" fname
if [ ! -f $fname ]
then
echo "The File $fname does not exist!"
exit 1
fi
echo "The File $fname exists."

Output:

Enter a File Name:myfile.txt
The File myfile.txt does not exist!

23. Check If a Directory Exists or Not

To check if a file is writable, use -d option with the variable that stores the directory inside a if block. For example, if dir is the variable that stores the directory to check, use -d $dir inside if block to check if it exists. Here’s how:

#!/bin/bash

read -p "Enter a File Name: " dir
if [ ! -d $dir ]
then
echo "The directory $dir does not exist!"
exit 1
fi
echo "The directory $dir exists."

Output:

Enter a File Name: bin
The directory bin exists.

24. Echo With New Line

To echo with a new line, use of the echo command with -e and \n before the message. That’s how:

#!/bin/bash

echo -e 'Hi\nthere!'

Output:

Hi
there!

25. Changing Internal Field Separator (IFS)/Delimiter

By changing the IFS you will be able to access values separated by your desired delimiter. First, store the default IFS in a variable using old_IFS = $IFS. Now, change IFS according to your preference and complete the task. At the end, restore the original IFS using IFS = $old_IFS. The below script shows how:

#!/bin/bash

#store default IFS
old_IFS= $IFS

IFS=,
read val1 val2 val3 <<< "5,60,70"
echo 1st value: $val1
echo 2nd value: $val2
echo 3rd value: $val3

#restore default IFS
IFS= $old_IFS;

Output:

1st value: 5
2nd value: 60
3rd value: 70

26. Take Two Command Line Arguments and Calculate their Sum

You can do direct mathematical operations on command line arguments using the $((..)).

#!/bin/bash

sum=$(( $1 + $2 ))
echo "The sum of $1 and $2 is $sum"

Syntax to Run Script >

bash misc_example3.sh 20 30

Output:

The sum of 20 and 30 is 50

27. Take Password Input

In bash, you can utilize the read command for taking password-type inputs. The application of the read with -sp option hides the input characters when you type them.

#!/bin/bash

read -sp "Enter your password: " pass
echo -e "\nYour password is: $pass"

Output:

Enter your password:
Your password is: linuxsimply

28. Take Timed Input

You can take timed input in bash using the read command with -t option. The prompt message will disappear if you do not complete entering your values within the specified time.

#!/bin/bash

read -t 5 -p "Enter your name within 5 seconds: " name

Output:

Enter your name within 5 seconds: Anonnya

29. Find the Length of a String

You can simply use the ${#STRING} to find the length of a string.

#!/bin/bash

str="My name is Tom!"
len=${#str}
echo "The length of the string is: $len"

Output:

The length of the string is: 15

30. Check if Two Strings are Equal

The String operators in Shell Scripting are as follows:

String Operators
< (Less than)	== (Equal)	+= (Concatenation)
> (Greater than)	!= (Not equal)

Check whether two strings are the same using the == (Equal) operator inside if condition.

#!/bin/bash

string1="hello"
string2="world"

if [ "$string1" == "$string2" ]; then
echo "The strings are equal."
else
echo "The strings are not equal."
fi

Output:

The strings are not equal.

31. Convert All Uppercase Letters in a String to Lowercase

To convert all upper-case letters in a string to lower-case letters, use the tr command with the [:upper:] and [:lower:] classes for conversion. Here is an example shows how to use it:

#!/bin/bash

read -p "Enter a string: " str
echo "Converted String:" $str | tr '[:upper:]' '[:lower:]'

Output:

Enter a string: ABCDefgh
Converted string: abcdefgh

32. Remove All Whitespace From a String

For removing white spaces from a string simply use the ${STRING// /}. Here’s how:

#!/bin/bash

str="   Hello    from Linuxsimply !   ! "
str=${str// /}
echo "The resultant string: $str"

Output:

The resultant string: HellofromLinuxsimply!!

33. Reverse a String

To reverse a string use the rev command with echo and Pipe(|). Here is a complete script showing how to reverse a string:

#!/bin/bash

str="Linuxsimply"
str=$(echo "$str" | rev)
echo "The reversed string: $str"

Output:

The reversed string: ylpmisxuniL

34. Reverse a Sentence

You can reverse a sentence by reversing the order of words with the awk command. Here’s how:

#!/bin/bash

sentence="Hello from LinuxsimplY!!"

r_sentence=$(echo "$sentence" | awk '{ for(i=NF;i>0;i--) printf("%s ",$i); print "" }')
echo "The reversed sentence is: $r_sentence"

Output:

The reversed sentence is: LinuxsimplY!! from Hello

35. Capitalize the First Letter of a Word

For capitalizing only the first letter of a word, first cut out the first letter by ${str:0:1}, then convert it using tr '[:lower:]' '[:upper:]', and finally concatenate it with the rest of the string. Here’s how:

#!/bin/bash

str="linuxsimply!!"
cap_str=$(echo "${str:0:1}" | tr '[:lower:]' '[:upper:]')${str:1}
echo "The capitalized word is: $cap_str"

Output:

The capitalized word is: Linuxsimply!!

36. Replace a Word in a Sentence

You can replace the first occurrence of a word in a string with a given word using the $(../../..).

#!/bin/bash

read -p "Enter a sentence: " str1
read -p "Enter the word to be replaced: " str2
read -p "Enter the new word: " str3
echo "Modified sentence: ${str1/$str2/$str3}"

Output:

Enter a sentence: I love Linux
Enter the word to be replaced: Linux
Enter the new word: Linuxsimply
Modified sentence: I love Linuxsimply

37. Print Numbers From 5 to 1

You can print a number sequence using the until loop in bash. In this case, specify the condition to stop the loop inside until [ ].

#!/bin/bash

n=5
until [ $n == 0 ]
do
echo $n
n=$((n-1))
done

Output:

38. Print Even Numbers From 1 to 10

To print only the even number in a range, check the even number condition inside the for loop before printing the number.

#!/bin/bash

for (( i=1; i<=10; i++ ))
do
if [ $((i%2)) == 0 ]
then
echo $i
fi
done

Output:

39. Print the Multiplication Table of a Number

Use the simple echo command inside a for loop to display the Multiplication Table of a number.

#!/bin/bash

read -p "Enter a number: " num
for (( i=1; i<10; i++ ))
do
echo "$num x $i = $((num*i))"
done

Output:

Enter a number: 12
12 x 1 = 12
12 x 2 = 24
12 x 3 = 36
12 x 4 = 48
12 x 5 = 60
12 x 6 = 72
12 x 7 = 84
12 x 8 = 96
12 x 9 = 108

40. Calculate the Sum of Digits of a Given Number

For calculating the sum of digits of a given number, extract each digit using the % operator and store the summation in a fixed variable using a loop.

#!/bin/bash

read -p "Enter a number: " num
sum=0
while [ $num -gt 0 ]
do
dig=$((num%10))
sum=$((sum+dig))
num=$((num/10))
done
echo "The sum of digits of the given number: $sum"

Output:

Enter a number: 1567
The sum of digits of the given number: 19

41. Calculate the Factorial of a Number

Calculate the factorial of a number by running multiplications inside a for loop.

#!/bin/bash

read -p "Enter a number: " num
temp=1
for (( i=1; i<=$num; i++ ))
do
temp=$((temp*i))
done
echo "The factorial of $num is: $temp"

Output:

Enter a number: 6
The factorial of 6 is: 720

42. Calculate the Sum of the First “n” Numbers

To calculate the sum of the first n numbers run a for loop and addition operation till n.

#!/bin/bash

read -p "Enter a number: " num
sum=0
for (( i=1; i<=$num; i++ ))
do
sum=$((sum + i))
done
echo "Sum of first $num numbers: $sum"

Output:

Enter a number: 100
Sum of first 100 numbers: 5050

43. Loop Through Array Elements

For accessing each array element you can use the for loop in the following manner. Indicate the desired array using ${ARRAY_NAME[@]} and access each item stored in the array.

#!/bin/bash
arr=("mango" "grape" "apple" "cherry" "orange")
for item in "${arr[@]}"; do
echo $item
done

Output:

mango
grape
apple
cherry
orange

44. Find the Smallest and Largest Elements in an Array

To find the smallest and largest element in a given array, first, initialize a small and a large number. Then compare the array elements with these numbers inside any loop. Here’s an example script showing how:

#!/bin/bash

arr=(24 27 84 11 99)

echo "Given array: ${arr[*]}"
s=100000
l=0
for num in "${arr[@]}"
do
if [ $num -lt $s ]
then
s=$num
fi
if [ $num -gt $l ]
then
l=$num
fi
done

echo "The smallest element: $s"
echo "The largest: $l"

Output:

Given array: 24 27 84 11 99
The smallest element: 11
The largest: 99

45. Sort an Array of Integers in Ascending Order

You can sort an array of integers by converting it into a list of integers using tr ‘\n’. The list of integers is sorted with the sort -n command and then converted back into an array.

#!/bin/bash

arr=(24 27 84 11 99)

echo "Given array: ${arr[*]}"
arr=($(echo "${arr[*]}" | tr ' ' '\n' | sort -n | tr '\n' ' '))
echo "Sorted array: ${arr[*]}"

Output:

Given array: 24 27 84 11 99
Sorted array: 11 24 27 84 99

46. Remove an Element From an Array

To remove an element from an array using the pattern substitution concept. The syntax ${arr[@]/$val} contains all the elements of the original array except for any occurrences of the value $val.

#!/bin/bash

arr=(24 27 84 11 99)

echo "Given array: ${arr[*]}"
read -p "Enter an element to remove: " val
arr=("${arr[@]/$val}")
echo "Resultant array: ${arr[*]}"

Output:

Given array: 24 27 84 11 99
Enter an element to remove: 11
Resultant array: 24 27 84  99

47. Inserting an Element Into an Array

For inserting an element into an array, split the array in the given index using ${arr[@]:0:$index} and insert the element. Here’s a complete script showing the process:

#!/bin/bash

arr=(24 27 84 11 99)

echo "Given array: ${arr[*]}"
read -p "Enter an element to insert: " new_val
read -p "Enter the index to insert the element: " index
arr=("${arr[@]:0:$index}" "$new_val" "${arr[@]:$index}")
echo "The updated array: ${arr[@]}"

Output:

Given array: 24 27 84 11 99
Enter an element to insert: 100
Enter the index to insert the element: 3
The updated array: 24 27 84 100 11 99

48. Slicing an Array Using Bash Script

Slice an array in Bash by placing the indices to slice inside the ${arr[@]:$index1:$index2} pattern.

#!/bin/bash

arr=(24 27 84 11 99)

echo "Given array: ${arr[*]}"
read -p "Enter 1st index of slice: " index1
read -p "Enter 2nd index of slice: " index2
sliced_arr=("${arr[@]:$index1:$index2}")
echo "The sliced array: ${sliced_arr[@]}"

Output:

Given array: 24 27 84 11 99
Enter 1st index of slice: 1
Enter 2nd index of slice: 3
The sliced array: 27 84 11

49. Calculate the Average of an Array of Numbers

Find the sum of array elements using a for loop and divide it by the number of elements i.e. ${#arr[@]}.

#!/bin/bash

echo "Enter an array of numbers (separated by space):"

read -a arr
sum=0
for i in "${arr[@]}"
do
sum=$((sum+i))
done
avg=$((sum/${#arr[@]}))
echo "Average of the array elements: $avg"

Output:

Enter an array of numbers (separated by space):
23 45 11 99 100
Average of the array elements: 55

50. Find the Length of an Array

To find the length of an array simply use the syntax: ${#arr[@]}.

#!/bin/bash

arr=(24 27 84 11 99)

echo "Given array: ${arr[*]}"
len=${#arr[@]}
echo "The length of the array: $len"

Output:

Given array: 24 27 84 11 99
The length of the array: 5

51. Check if a String is a Palindrome

You can write the code to check a palindrome inside the function Palindrome() and call it by passing the desired string:

#!/bin/bash

Palindrome () {

s=$1
if [ "$(echo $s | rev)" == "$str" ]
then
echo "The string is a Palindrome"
else
echo "The string is not a palindrome"
fi
}
read -p "Enter a string: " str
Palindrome "$str"

Output:

Enter a string: wow
The string is a Palindrome

The rules for Function in Shell Scripting are as follows:

Functions must be defined before using/calling them.
You may pass arguments to functions while calling them.
To access arguments inside the function, use $1, $2, $3 … and so on according to the number and sequence of arguments passed.
The scope of the variables declared inside a function remains within the function.

52. Check if a Number is Prime

Create the Prime() function that returns whether the parameter passed is prime or not. Here is the script:

#!/bin/bash

Prime () {
num=$1
if [ $num -lt 2 ]
then
echo "The number $num is Not Prime"
return
fi
for (( i=2; i<=$num/2; i++ ))
do
if [ $((num%i)) -eq 0 ]
then
echo "The number $num is Not Prime"
return
fi
done
echo "The number $num is Prime"
}
read -p "Enter a number: " num
Prime "$num"

Output:

Enter a number: 2
The number 2 is Prime

53. Convert Fahrenheit to Celsius

Here, the function Celsius() runs the necessary formula on the passed temperature value in Fahrenheit to convert it into Celsius. Here is the script:

#!/bin/bash

Celsius () {
f=$1
c=$((($f-32)*5/9))
echo "Temperature in Celsius = $c°C"
}

read -p "Enter temperature in Fahrenheit:" f
Celsius $f

Output:

Enter temperature in Fahrenheit:100
Temperature in Celsius = 37°C

54. Calculate the Area of a Rectangle

Write the formula to calculate the area of a rectangle inside the function Area() and call it by passing the height and width.

#!/bin/bash

Area() {
width=$1
height=$2
area=$(($width * $height))
echo "Area of the rectangle is: $area"
}

read -p "Enter height and width of the ractangle:" h w
Area $h $w

Output:

Enter height and width of the ractangle:10 4
"Area of the rectangle is: 40"

55. Calculate the Area of a Circle

Write the formula to calculate the area of a circle inside the function Area() and call it by passing the given radius.

#!/bin/bash

Area () {
radius=$1
area=$(echo "scale=2; 3.14 * $radius * $radius" | bc)
echo "Area of a circle with radius $radius is $area."
}

read -p "Enter radius of the circle:" r
Area $r

Output:

Enter radius of the circle:4
Area of a circle with radius 4 is 50.24.

56. Calculate Grade with Number

The function Grade() runs the necessary conditions to divide the number ranges into grades and returns the resultant grade.

Grade() {
score=$1
if (( $score >= 80 )); then
grade="A+"
elif (( $score >= 70 )); then
grade="A"
elif (( $score >= 60 )); then
grade="B"
elif (( $score >= 50 )); then
grade="C"
elif (( $score >= 40 )); then
grade="D"
else
grade="F"
fi
echo "The grade for mark $s is $grade"
}

read -p "Enter a score between 1-100:" s
Grade $s

Output:

Enter a score between 1-100:76
"The grade for mark 76 is A"

57. Search for a Pattern Inside a File

The script given below will take a filename and a pattern as user input and search it within the file. If the pattern is found then the lines having the pattern will be displayed on the screen along with line numbers. Otherwise, it will print a message saying the pattern did not match.

#!/bin/bash

read -p "Enter filename: " filename
read -p "Enter a pattern to search for: " pattern
grep -w -n $pattern $filename
if [ $? -eq 1 ]; then
echo "Pattern did not match."
fi

Output:

Enter filename: poem.txt
Enter a pattern to search for: daffodils
4:A host, of golden daffodils;
27:And dances with the daffodils.

58. Replace a Pattern in a Fille

The following script will take a file name and a pattern from the user to replace it with a new pattern. Finally, it will display the updated lines on the terminal. If the pattern to replace does not exist, then it will show an error message.

#!/bin/bash

read -p "Enter filename: " filename
read -p "Enter a pattern to replace: " pattern
read -p "Enter new pattern: " new_pattern
grep -q $pattern $filename
if [ $? -eq 0 ]; then
sed -i "s/$pattern/$new_pattern/g" $filename
echo "Updated Lines: "
grep -w -n $new_pattern $filename
else
echo "Error! Pattern did not match."
fi

Output:

Enter filename: poem.txt
Enter a pattern to replace: daffodils
Enter new pattern: dandelions
Updated Lines:
4:A host, of golden dandelions;
27:And dances with the dandelions.

59. Print Contents of Multiple Files

The below script is for reading the contents of multiple files. It will take the file names as user input and display their contents on the screen. If any filename does not exist, it will show a separate error message for that file.

#!/bin/bash

read -p "Enter the file names: " files
IFS=' ' read -ra array <<< "$files"
for file in "${array[@]}"
do
if [ -e "$file" ]; then
echo "Contents of $file:"
cat "$file"
else
echo "Error: $file does not exist"
fi
done

Output:

Enter the file names: message.txt passage.txt

Contents of message.txt:

“Merry Christmas! May your happiness be large and your bills be small.”

Contents of passage.txt:

The students told the headmaster that they wanted to celebrate the victory of the National Debate Competition.

60. Copy a File to a New Location

You can copy a file to another location using the bash script below. It will read the filename and destination path from the terminal and copy the file if it exists in the current directory. If the file is not there, the script will return an error message.

#!/bin/bash

read -p "Enter the file name: " file
read -p "Enter destination path:" dest

if [ -e "$file" ]; then
cp $file $dest
file_location=$(readlink -f $dest)
echo "A copy of $file is now located att: $file_location"
else
echo "Error: $file does not exist"
fi

Output:

Enter the file name: poem.txt
Enter destination path:/home/anonnya/Documents

A copy of poem.txt is now located at: /home/anonnya/Documents

61. Create a New File and Write Text Inside

The script given below is for creating a new file and writing text inside the file. You will be able to write into the file from the command line. Upon completion, it will show a message saying the file has been created.

#!/bin/bash

read -p "Enter the file name: " file
echo "Enter text to write:"
read text
echo "$text" > "$file"
echo "-----------------------------------"
echo "The File $file is created!"

Output:

Enter the file name: text_file1.txt
Enter text to write:

In English, there are three articles: a, an, and the. Articles are used before nouns or noun equivalents and are a type of adjective. The definite article (the) is used before a noun to indicate that the identity of the noun is known to the reader.

-----------------------------------

The File text_file1.txt is created!

62. Compare the Contents of Two Given Files

The following bash script takes two file names as user input and compares their contents. If one or either of the files does not exist in the current directory it shows an error to the user. Otherwise prints the result if the files are identical or not.

#!/bin/bash

read -p "Enter the 1st file name: " file1
read -p "Enter the 2nd file name: " file2

if [ ! -f $file1 ] || [ ! -f $file2 ]
then
echo "Error! One of the files does not exists."
exit 1
fi
if cmp -s "$file1" "$file2"
then
echo "The Files $file1 and $file2 are identical."
else
echo "The Files $file1 and $file2 are different."
fi

Output:

Enter the 1st file name: article1.txt
Enter the 2nd file name: text_file1.txt

The Files article1.txt and text_file1.txt are identical.

63. Delete a Given File If It Exists

To check if a file exists, use -f followed by the variable that holds the filename to check. Then remove it with rm command if -f $file is true.

#!/bin/bash

read -p "Enter the file name for deletion: " file

if [ -f $file ]
then
rm $file
echo "The file $file deleted successfully!"
else
echo "Error! The file $file does not exist."
fi

Output:

Enter the file name for deletion: article1.txt

The file article1.txt deleted successfully!

64. Rename a File

All you have to do is enter the old filename and the new filename. The script will rename the file if it is available in the directory. If the file is not in the path, then it will display an error message. You can rename an existing file using the script below:

#!/bin/bash

read -p "Enter the file name: " file
read -p "Enter new file name: " new_file

if [ -f $file ]
then
mv "$file" "$new_file"
echo "The file $file has been renamed as $new_file!"
else
echo "Error! The file $file does not exist."
fi

Output:

Enter the file name: poem.txt
Enter new file name: daffodils.txt

The file poem.txt has been renamed as daffodils.txt!

65. Check the Permissions of a File

Use -r for readability check, -w for writeability check, and -x for excitability check. The script below checks permissions for the given filename and lists the active permissions of the current user:

#!/bin/bash

read -p "Enter the file name: " file

if [ -f $file ]; then
if [ -r "$file" ]; then
echo "Readable"
fi
if [ -w "$file" ]; then
echo "Writable"
fi
if [ -x "$file" ]; then
echo "Executable"
fi
else
echo "Error! The file $file does not exist."
fi

Output:

Enter the file name: daffodils.txt
Readable
Writable

66. Sets the Permissions of a Directory for the Owner

Use -d $dir to check if the directory exists. Then use chmod u+rx $dir to set writing and executing permission of the directory for the user. Below is the complete script of doing the task:

#!/bin/bash

read -p "Enter the directory name: " dir

if [ -d $dir ]; then
chmod u+rwx $dir
echo "Directory permissions have been updated!"
else
echo "Error! The directory $dir does not exist."
fi

Output:

Enter the directory name: Documents
Directory permissions have been updated!

67. Change the File Owner

Use chown command to change the ownership of a file. The script here changes the owner of a file if the file exists in the directory. Since changing ownership requires administrator permissions, you will need to give the sudo password while running the script below:

#!/bin/bash

read -p "Enter the file name: " file
read -p "Enter file owner name: " owner

if [ -f $file ]; then
sudo chown $owner $file
echo "Changed file owner to $owner!"
else
echo "Error! The file $file does not exist."
fi

Output:

Enter the file name: daffodils.txt
Enter file owner name: tom

[sudo] password for anonnya:

Changed file owner to tom!

68. Change the Overall Permissions of a File

You can change the permissions of an existing file using the script below. All you have to do is enter the filename, the permissions in absolute mode, and the sudo password to activate administrative privileges. The script will update the file permissions if it is available in the directory. If the file is not in the path, then it will display an error message. Here is the script:

#!/bin/bash

read -p "Enter the file name: " file
read -p "Enter new permissions in Absolute Mode: " permissions

if [ -f $file ]; then
sudo chmod $permissions $file
echo "Permissions for the file $file has been changed!"
else
echo "Error! The file $file does not exist."
fi

Output:

Enter the file name: daffodils.txt
Enter new permissions in Absolute Mode: 777

[sudo] password for anonnya:

Permissions for the file daffodils.txt has been changed!

69. Check a Remote Host for its Availability

The following script checks the network status of a remote host. You will need to enter the host IP address as input and it will return a message saying if the host is up or down.

#!/bin/bash

read -p "Enter remote host IP address:" ip

ping -c 1 $ip
if [ $? -eq 0 ]
then
echo "-----------------------"
echo "Host is up!"
echo "-----------------------"
else
echo "-----------------------"
echo "Host is down!"
echo "-----------------------"
fi

Output:

Enter remote host IP address:192.168.0.6

PING 192.168.0.6 (192.168.0.6) 56(84) bytes of data.
64 bytes from 192.168.0.6: icmp_seq=1 ttl=64 time=4.10 ms
--- 192.168.0.6 ping statistics ---

1 packets transmitted, 1 received, 0% packet loss, time 0ms

rtt min/avg/max/mdev = 4.095/4.095/4.095/0.000 ms
-----------------------
Host is up!
-----------------------

70. Test if a Remote Port is Open

Takes a host address and port number as the input. If the connection to the host through the port number is successful then it verifies that the port is open. The script below checks the network connection in a system port:

#!/bin/bash

read -p "Enter host address:" HOST
read -p "Enter port number:" PORT

nc -z -v -w5 "$HOST" "$PORT"

if [ $? -eq 0 ]; then
echo "----------------------------------------------"
echo "Port $PORT on $HOST is open"
echo "----------------------------------------------"
else
echo "----------------------------------------------"
echo "Port $PORT on $HOST is closed"
echo "----------------------------------------------"
fi

Output:

Enter host address:192.168.0.107
Enter port number:80

Connection to 192.168.0.107 80 port [tcp/http-alt] succeeded!
----------------------------------------------
Port 80 on 192.168.0.107 is open
----------------------------------------------

71. Checking Network Connectivity

Use the ping command to check network connectivity. The below script checks network connectivity to a remote host via the internet. If there is a successful connection then it returns the status “Internet connection is up”. Otherwise, returns “Internet connection is down”.

#!/bin/bash

read -p "Enter a host address:" HOST

if ping -q -c 1 -W 1 $HOST >/dev/null; then
echo "----------------------------------------------"
echo "Internet connection is up"
echo "----------------------------------------------"
else
echo "----------------------------------------------"
echo "Internet connection is down"
echo "----------------------------------------------"
fi

Output:

Enter a host address:192.168.0.107
----------------------------------------------
Internet connection is up
----------------------------------------------

72. Automating Network Configuration

The following bash script configures a network IP address and subnet mask. Upon configuration, it sets up the gateway and DNS server at the given addresses. All four IP addresses are passed as user input. It will return an error message if it is unsuccessful at running any of the commands.

#!/bin/bash

echo "Enter network configuration variables:"
read -p "Enter an IP address: " ip_addr
read -p "Enter a subnet mask: " subnet_mask
read -p "Enter a Gateway address: " gateway
read -p "Enter a DNS address: " dns

# Configure network interface
sudo ifconfig eth0 $ip_addr netmask $subnet_mask up
if [ $? -eq 0 ]; then

# Set default gateway
sudo route add default gw $gateway
if [ $? -eq 0 ]; then

# Set DNS servers
sudo echo "nameserver $dns" > /etc/resolv.conf
if [ $? -eq 0 ]; then
echo "----------------------------------------------"
echo "Network configuration completed"
echo "----------------------------------------------"
else
echo "----------------------------------------------"
echo "Error while setting the DNS server."
fi
else
echo "----------------------------------------------"
echo "Error while setting the default gateway."
fi
else
echo "----------------------------------------------"
echo "Network Configuration Failed."
fi

Note: If ipconfig is not installed in your system, install it using:

sudo apt install ipconfig

Output:

Enter network configuration variables:
Enter an IP address: 192.168.0.108
Enter a subnet mask: 255.255.255.0
Enter a Gateway address: 192.168.0.1
Enter a DNS address: 8.8.8.8
----------------------------------------------
Network configuration completed
----------------------------------------------

73. Check if a Process is Running

Use pgrep to check if a process is currently running on your system or not. The below script shows an example how to use it:

#!/bin/bash

read -p "Enter process name: " process

if pgrep $process > /dev/null
then
echo "Process is running."
else
echo "Process is not running."
fi

Output:

Enter process name: bash 
Process is running.

74. Start a Process if It’s Not Running

Check if the process is not running using ! pgrep. Then pass the process name as user input to start it. The script below to start a not running process:

#!/bin/bash

read -p "Enter process name: " process

if ! pgrep $process > /dev/null
then
/path/to/process_name &
echo "The Process $process has now started."
else
echo "The Process is already running."
fi

Output:

Enter process name: bash
The Process is already running.

75. Stop a Running Process

Use pkill command to stop a running process. The script below can stop a process if it runs in the system:

#!/bin/bash

read -p "Enter process name: " process

if pgrep $process > /dev/null
then
pkill $process
echo "The Process $process has stopped."
else
echo "The Process $process is not running."
fi

Output:

Enter process name: nslookup
The Process nslookup has stopped.

76. Restart a Process

Use the following script aims to take a process name as input and then restart it:

#!/bin/bash

read -p "Enter process name: " process

pid=$(pgrep -f $process)
if [ -n "$pid" ]; then
kill $pid
sleep 5
if pgrep -f $process> /dev/null; then
echo "Process did not exit properly, force killing..."
kill -9 $pid
fi
fi
process_path=$(which $process)
$process_path & echo "Process restarted."

If the process is already running then the script kills the process and starts over. After the first kill command, it waits for 5 seconds. If by then the process does not terminate then it will force kill that process before restarting.

Output:

Enter process name: firefox
Process restarted.

77. Monitor a Process and Restart If It Crashes

The script here takes a process name as input from the user and checks for its status every 5 seconds:

#!/bin/bash

read -p "Enter process name: " process

process_path=$(which $process)
while true
do
if pgrep $process > /dev/null
then
echo "The Process $process is running."
sleep 5
else
$process_path &
echo "The Process $process restarted."
continue
fi
done

Output:

Enter process name: firefox

The Process firefox is running.
The Process firefox is running.

78. Display the Top 10 CPU-Consuming Processes

The script below lists the top 10 CPU-consuming processes and prints the Process ID, the percentage of CPU usage along with the command that runs each process:

#!/bin/bash

echo "The current top 10 CPU-consuming processes: "
ps -eo pid,%cpu,args | sort -k 2 -r | head -n 11

79. Display the Top 10 Memory-Consuming Processes

The given script lists the top 10 memory-consuming processes and prints the Process ID, percentage of memory usage as well as the commands for running each process:

#!/bin/bash

echo "The current top 10 Memory-consuming processes: "
ps -eo pid,%mem,args | sort -k 2 -r | head -n 11

80. Kill Processes of a Specific User

Use pkill -u followed by the username to kill all process of the user. The following script is created to kill all the processes of a specific user:

#!/bin/bash

read -p "Enter username: " user

sudo pkill -u $user
echo "All processes of user $user have been terminated."

Output:

Enter username: tom
[sudo] password for anonnya:

All processes of user tom have been terminated.

81. Kill All Processes That are Consuming More Than a Certain Amount of CPU

Use the script below to kill all processes that are consuming more than a certain amount of CPU:

#!/bin/bash

read -p "Enter CPU usage threshold: " threshold

if [ "$(ps -eo pid,%cpu | awk -v t=$threshold '$2 > t {print $1}' | wc -c)" -gt 0 ]; then
for pid in $(ps -eo pid,%cpu | awk -v t=$threshold '$2 > t {print $1}')
do
kill $pid
done
echo "All processes consuming more than $threshold% CPU killed."
else
echo "There are no process consuming more than $threshold% CPU."
fi

This script takes a CPU usage percentage as user input and terminates all the running processes that are consuming more than the entered CPU threshold. If there is no process above that threshold, then it returns a message saying there are no such processes.

82. Kill All Processes That are Consuming More Memory

Use the script below to kill all processes that are consuming more than a certain amount of memory:

#!/bin/bash

read -p "Enter memory usage threshold (in KB): " threshold

if [ "$(ps -eo pid,%mem | awk -v t=$threshold '$2 > t {print $1}' | wc -c)" -gt 0 ]; then
for pid in $(ps -eo pid,%mem | awk -v t=$threshold '$2 > t {print $1}')
do
kill $pid
done
echo "All processes consuming more than $threshold KB memory killed."
else
echo "There are no process consuming more than $threshold KB memory."
fi

This script takes a memory space percentage as user input and terminates all the running processes that are consuming more than the entered space threshold. If there is no process above that threshold, then it returns a message saying there are no such processes.

83. Check the Number of Logged-in Users

Use who command to check logged-in users. Then use a pipe with wc -l to count the number of users. Here’s how:

#!/bin/bash

users=$(who | wc -l)
echo "Number of currently logged-in users: $users"

84. Check Operating System Information

The following script displays information regarding the machine’s operating system:

#!/bin/bash

os_name=$(uname -s)
os_release=$(uname -r)
os_version=$(cat /etc/*-release | grep VERSION_ID | cut -d '"' -f 2)
os_arch=$(uname -m)

echo "OS Name: $os_name"
echo "OS Release: $os_release"
echo "OS Version: $os_version"
echo "OS Architecture: $os_arch"

It retrieves and lists the os name, release, version as well as system architecture.

Output:

OS Name: Linux
OS Release: 5.19.0-38-generic
OS Version: 22.04
OS Architecture: x86_64

85. Check the System’s Memory Usage

The script given below calculates the percentage of memory being used:

#!/bin/bash

mem=$(free -m | awk 'NR==2{printf "%.2f%%", $3*100/$2}')
echo "Current Memory Usage: $mem"

The $3*100/$2 expression converts the usage into percentages and displays the output with two decimal places.

86. Check the System’s Disk Usage

Use df command to check disk usage. The following script displays the percentage of disk space used on the root (/) file system:

#!/bin/bash

disk=$(df -h | awk '$NF=="/"{printf "%s", $5}')
echo "Current Disk Usage: $disk"

87. Check the System’s Network Information

Use the script below to get the network information of your system:

#!/bin/bash

echo " System’s network information:-"

ip=$(hostname -I)
echo "IP Address: $ip"
gw=$(ip route | awk '/default/ { print $3 }')
echo "Gateway: $gw"
dns=$(grep "nameserver" /etc/resolv.conf | awk '{print $2}')
echo "DNS Server: $dns"

It lists the system’s IP address, Gateway address, and DNS server address.

Output:

System’s network information:-

IP Address: 192.168.0.109
Gateway: 192.168.0.1
DNS Server: 127.0.0.53

88. Check the Uptime

Use uptime command to find out the uptime of the system. Here’s an example script:

#!/bin/bash

uptime | awk '{print $1,$2,$3}' | sed 's/,//'
echo "Uptime: $uptime"

The given script can be used to find out the uptime of the system. It will return two values. The first one is the current time, and the second one is the uptime i.e. for how long the system has been running.

89. Check the System Load Average

The following script returns the system’s Load Average:

#!/bin/bash

loadavg=$(uptime | awk '{print $10,$11,$12}')
echo "Load Average: $loadavg"

It will extract the load averages for the past 1, 5, and 15 minutes from the system’s uptime and display their average on the screen.

90. Check the System Architecture

To determine your current machine’s architecture, use uname -m. Here’s how:

#!/bin/bash

arch=$(uname -m)
echo "System Architecture: $arch"

Output:

System Architecture: x86_64

91. Count the Number of Files in the System

You can use the script below to find the available number of files on your machine:

#!/bin/bash

count=$(find / -type f | wc -l)
echo "Number of files in the system: $count."

It runs the find command to check every file on the system and returns the total file count.

92. Automated Backup with Bash

The following script creates a backup file of a given directory:

#!/bin/bash

read -p "Enter path of the directory to backup: " source_dir
read -p "Enter destination path for backup: " backup_dir

date=$(date +%Y-%m-%d)
backup_file="backup-$date.tar.gz"

# Create backup directory if it doesn't exist
if [ ! -d "$backup_dir" ]; then
mkdir -p "$backup_dir"
fi

# Create backup archive
tar -czf "$backup_dir/$backup_file" "$source_dir"
echo "Completed Creating backup at: $backup_dir."

Here, The source directory path and the destination directory path are user inputs. The backup file is named along with the current date for keeping track. Upon completion of the task, it returns the path where the backup archive resides.

Output:

Enter path of the directory to backup: /home/anonnya/Documents
Enter destination path for backup: /home/anonnya/Desktop
tar: Removing leading `/' from member names
Completed Creating backup at: /home/anonnya/Desktop.

93. Generate Alert if Disk Space Usage Goes Over a Threshold

The script below generates an alert if the disk space usage goes over a threshold. It takes the threshold and a filename from the user. The alert is then generated in that file along with the disk space usage. If the space consumed is less than the threshold then the file remains empty.

#!/bin/bash

read -p "Enter filename to write alert: " file
touch $file
read -p "Enter disk space threshold: " threshold
df -H | grep -vE "^Filesystem|tmpfs|cdrom" | awk '{ print $5 " " $1 }' | while read output;
do
usage=$(echo $output | awk '{ print $1}' | cut -d'%' -f1)
if [ $usage -ge $threshold ]; then
partition=$(echo $output | awk '{ print $2 }')
echo "Alert for \"$partition: Almost out of disk space $usage% as on $(date) " >> $file
break
fi
done
cat $file

94. Create a New User and Add It to the Sudo Group

Use useradd command with -m -s option to create a new user and add it to the sudo group. he below script shows how:

#!/bin/bash

read -p "Enter username: " username
read -p "Enter password: " password

useradd -m -s /bin/bash -p $(openssl passwd -1 $password) $username
if [ $? -eq 0 ]; then
usermod -a -G sudo $username

mkdir /home/$username/mydir
chown -R $username:$username /home/$username/mydir
usermod -d /home/$username/mydir $username

echo "$username ALL=(ALL) NOPASSWD:ALL" >> /etc/sudoers

echo "User $username created successfully!"
echo "User $username added to sudo group!"
else
echo "Error while creating user!"
fi

The script will take the username and password as input to create the user. It will also create a home directory for the user besides adding the account to the sudo group.

Output:

Enter username: Jim
Enter password: linuxsimply

User Jim created successfully!
User Jim added to sudo group!

95. Monitor Network Traffic

The following script monitors the receiving (RX) and transmitting(TX) packets over a network. Enter the interface name that you want to monitor. Then every 10 seconds, it will display the total packets received and transmitted and their size in KB.

#!/bin/bash

read -p "Enter network interface to monitor traffic (ex. eth0): " net

while true
do
rx=$(ifconfig $net | grep "RX packets" | awk '{print $3 $6 $7}')
tx=$(ifconfig $net | grep "TX packets" | awk '{print $3 $6 $7}')
echo "$(date) RX: $rx, TX: $tx"
sleep 10
done

Output:

Enter network interface to monitor traffic (ex. eth0): ens33

Wed May 10 16:55:40 +06 2023 RX: 342(40.4KB), TX: 171(18.4KB)
Wed May 10 16:55:51 +06 2023 RX: 355(41.6KB), TX: 178(19.0KB)
Wed May 10 16:56:01 +06 2023 RX: 361(42.0KB), TX: 178(19.0KB)
Wed May 10 16:56:11 +06 2023 RX: 361(42.0KB), TX: 178(19.0KB)

96. Monitor CPU and Memory Usage

The script below can be used to monitor the CPU and Memory usage of a system. It extracts the CPU and Memory usage information every 10 seconds and converts them into a percentage for displaying on the screen.

#!/bin/bash

while true
do
cpu=$(top -bn1 | grep "Cpu(s)" | sed "s/.*, *\([0-9.]*\)%* id.*/\1/" | awk '{print 100 - $1"%"}')
mem=$(free -m | awk 'NR==2{printf "%.2f%%", $3*100/$2 }')
echo "$(date) CPU Usage: $cpu, Memory Usage: $mem"
sleep 10
done

97. Creating a Script and Adding It to PATH

You can use the script below to customize another script and make it runnable. The script here will take another script name and the commands to write within this new script as user inputs. After receiving the input values, it will update the permission modes of the desired script and add it to the $PATH variable to make the new script runnable. After creation, you can run this new script with the bash keyword.

#!/bin/bash

read -p "Enter a name for the command: " my_comm
echo "Enter commands to write on script:"
read comm
read -p "Enter path to the directory containing the command: " comm_path

# Create script for custom command
echo "#!/bin/bash" > $my_comm.sh
echo "$comm" >> $my_comm.sh

# Make script executable
chmod +x $my_comm.sh

# Add script to PATH
export PATH="$PATH$comm_path/$my_comm.sh"

echo "A script called $my_comm has been created."

Output:

Enter a name for the command: echo_hello
Enter commands to write on script:

echo "Hello from custom command!!"

Enter path to the directory containing the command: /home/anonnya/bin

A script called echo_hello has been created.

98. Running a Command At Regular Intervals

Use crontab to run a command at regular intervals. The script given below runs a command at regular time intervals:

#!/bin/bash

read -p "Enter command to run: " com
command_to_run=$(which $com)
read -p "Enter interval for running the command (m h dom mon dow): " interval

# Add command to crontab
(crontab -l ; echo "$interval $command_to_run") | sort - | uniq - | crontab -
echo "Command added to crontab and will run at $interval"

To achieve this task the user has to enter the desired command and the interval for running that command. The interval passed as input must be in the following format: m h dom mon dow.

99. Downloading Files From a List of URLs Using Bash

Use curl -o command followed by the filename and URL to download files form the URL. Here’s an example script:

#!/bin/bash

read -p "Enter the filename containing URLs: " url_file

while read -r url; do
filename=$(basename "$url")
curl -o "$filename" "$url"
echo "Completed Download $filename"
done < "$url_file"
echo "--------------------------------------------------------------------------------------------"
echo "All files downloaded successfully!"

The following script takes a filename as input where a list of URLs should be stored. The script will iterate through the list of URLs and download the available contents on the link. It displays each download information on the terminal along with the “Completed Download” message. Upon downloading files from all the URLs, it shows another message saying “All files downloaded successfully!”.

100. Organize a Directory Based on File Types

The script given below organizes files in a directory depending on their type. The user needs to give a destination directory path to organize the files along with the source directory path.

#!/bin/bash

# Specify the source and destination directories
read -p "Enter path to the source directory: " source_dir
read -p "Enter path to the destination directory: " dest_dir

# Create the destination directories if they don't exist
mkdir -p "${dest_dir}/Documents"
mkdir -p "${dest_dir}/Images"
mkdir -p "${dest_dir}/Music"
mkdir -p "${dest_dir}/Videos"
mkdir -p "${dest_dir}/Others"

# Move files to the appropriate directories based on their extensions
for file in "${source_dir}"/*; do
if [ -f "${file}" ]; then
extension="${file##*.}"
case "${extension}" in
txt|pdf|doc|docx|odt|rtf)
mv "${file}" "${dest_dir}/Documents"
;;
jpg|jpeg|png|gif|bmp)
mv "${file}" "${dest_dir}/Images"
;;
mp3|wav|ogg|flac)
mv "${file}" "${dest_dir}/Music"
;;
mp4|avi|wmv|mkv|mov)
mv "${file}" "${dest_dir}/Videos"
;;
*)
mv "${file}" "${dest_dir}/Others"
;;
esac
fi
done
echo "Files organized successfully!"

This script will create five directories: 1) Documents, 2) Images, 3) Music, 4) Videos, and 5) Others only if they do not already exist on the destination path. Then, it will check all the files and their extension and move them to the corresponding directory. If there is any unknown file extension, then the script will move the file to the Others Directory.

Conclusion

This article covers 100 shell script examples that a user can frequently use. These examples range from basic to advanced topics along with the preliminary concepts of script writing and configurations. Furthermore, the examples are divided into sections and subsections depending on their topic and level of understanding. Therefore, it is a proper guide for users of every category.