Linux Shell Script | Programs and Examples
Linux Shell Script Programs – Sample Code
Sample programs is the first step you take to transition from theory to practical. These Linux Shell Script Programs are demonstrated in a classroom will ensure you are able to immediately see it running in front of your eyes. Added to that our mentors will provide you some exercises where you will be modifying the code in the class itself. By doing this fill-in-the-blanks approach, will take out your fear of coding and start taking your next step towards skill development.
Linux - BASH Shell Scripting - sample programs
Brief:
A simple script to print Hello World on terminal using echo command
Source Code:
#!/bin/bash
#
# Author : Emertxe (http://www.emertxe.com)
# Date : Tue 16 Feb 2016 16:27:07 IST
# File : ls_001_ch6_hello_world.sh
# Title : Hello World
# Description : A simple script to print Hello World on terminal using echo command
#
echo "Hello World"Example output:
Brief:
A simple script to print the calender month by default.
Source Code:
#!/bin/bash
#
# Author : Emertxe (http://www.emertxe.com)
# Date : Tue 16 Feb 2016 16:27:07 IST
# File : ls_002_ch6_calender.sh
# Title : Calender
# Description : A simple script to print the calender month by default
#
echo "The Month is"
cal # cal command displays current month by default
echo "An alternate view of calender"
ncal # An alternale layout for calender
Example output:
Brief:
A simple script to read user input and perform operations with them.
Source Code:
#!/bin/bash
#
# Author : Emertxe (http://www.emertxe.com)
# Date : Tue 16 Feb 2016 16:27:07 IST
# File : ls_003_ch6_variables_and_expressions.sh
# Title : Variables and Expressions
# Description : A simple script to read user input and perform operations with them
#
echo -n "Enter number 1 : " # -n option supresses newline
read NUM1 # Read the user input from Standard Input and store in Variable NUM1
echo -n "Enter number 2 : "
read NUM2
SUM=$(($NUM1 + $NUM2)) # Arithmetic expansion using double parentheses
echo "The sum is $SUM"
SUM=`expr $NUM1 + $NUM2` # Arithmetic expansion using backticks.
#Usage of expr command to evaluate the expression
echo "The sum is $SUM"Example output:
Brief:
A script to show usage of if condition
Source Code:
#!/bin/bash
#
# Author : Emertxe (http://www.emertxe.com)
# Date : Tue 16 Feb 2016 16:27:07 IST
# File : ls_004_ch6_if.sh
# Title : Test construct - if
# Description : A script to show usage of if condition
#
NUM1=5 # variable assignment
NUM2=2
if [ $NUM1 -gt $NUM2 ] # -gt is to test integer numbers
then
echo "NUM1 > NUM2"
fiExample output:
Brief:
A script to show usage of if else condition
Source Code:
#!/bin/bash
#
# Author : Emertxe (http://www.emertxe.com)
# Date : Tue 16 Feb 2016 16:27:07 IST
# File : ls_005_ch6_if_else.sh
# Title : Test construct - if else
# Description : A script to show usage of if else condition
#
NUM1=2 # Variable assignment
NUM2=5
if [ $NUM1 -lt $NUM2 ] # -lt is to test integer numbers
then
echo "NUM1 < NUM2" else echo "NUM1 > NUM2"
fiExample output:
Brief:
A script to show usage of else if condition
Source Code:
#!/bin/bash
#
# Author : Emertxe (https://www.emertxe.com)
# Date : Tue 16 Feb 2016 16:27:07 IST
# File : ls_006_ch6_elif.sh
# Title : Test construct - elif (else if)
# Description : A script to show usage of else if condition
#
echo -n "Enter a number: "
read NUM
if [ $NUM -gt 0 ]
then
echo "$NUM is +ve"
elif [ $NUM -lt 0 ]
then
echo "$NUM is -ve"
else
echo "$NUM is 0"
fi
echo "done"
Example output:
Brief:
A script to demonstrate case statement
Source Code:
#!/bin/bash
#
# Author : Emertxe (https://www.emertxe.com)
# Date : Tue 16 Feb 2016 16:27:07 IST
# File : ls_007_01_ch6_switch_case.sh
# Title : Test and Branch constuct - Case
# Description : A script to demonstrate case statement
#
echo -n "Enter a character: "
read CHAR
case $CHAR in
a) echo "You entered $CHAR which is a vowel";; # ;; Terminates each option
e) echo "You entered $CHAR which is a vowel";;
i) echo "You entered $CHAR which is a vowel";;
o) echo "You entered $CHAR which is a vowel";;
u) echo "You entered $CHAR which is a vowel";;
*) echo "You entered $CHAR which is not a vowel";; # Defaults to everything else
esac
echo "What if you enter upper case letters!!?, Check the next example"
Example output:
Brief:
A script to demonstrate case statement
Source Code:
#!/bin/bash
#
# Author : Emertxe (https://www.emertxe.com)
# Date : Tue 16 Feb 2016 16:27:07 IST
# File : ls_007_02_ch6_switch_case.sh
# Title : Test and Branch constuct - Case
# Description : A script to demonstrate case statement
#
echo -n "Enter a character: "
read CHAR
case $CHAR in
a | A) # Test for both Lower or Upper case letter
# You may write commands in this fashion too!!, means multiline commands
echo "You entered $CHAR which is a vowel"
;; # Terminates each option
e | E)
echo "You entered $CHAR which is a vowel"
;;
i | I)
echo "You entered $CHAR which is a vowel"
;;
o | O)
echo "You entered $CHAR which is a vowel"
;;
u | U)
echo "You entered $CHAR which is a vowel"
;;
*) # Defaults to everything else
echo "You entered $CHAR which is not a vowel"
;;
esacExample output:
Brief:
A script to demonstrate case statement
Source Code:
#!/bin/bash
#
# Author : Emertxe (https://www.emertxe.com)
# Date : Tue 16 Feb 2016 16:27:07 IST
# File : ls_007_03_ch6_switch_case.sh
# Title : Test and Branch constuct - Case
# Description : A script to demonstrate case statement with string inputs
#
echo -n "Oceans are larger than lakes (True or False) : "
read USER_INPUT
case $USER_INPUT in
"TRUE"| "True" | "true")
echo "Yes you are right"
;; # Terminates each option
"FALSE" | "Fasle" | "false")
echo "No your are wrong"
;;
*) # Defaults to everything else
echo "Please enter either True or False"
;;
esacExample output:
Brief:
A simple script to show usage of string compare operator = and !=
Source Code:
#!/bin/bash
#
# Author : Emertxe (https://www.emertxe.com)
# Date : Tue 16 Feb 2016 16:27:07 IST
# File : ls_008_01_ch6_stings.sh
# Title : Operators - String Compare
# Description : A simple script to show usage of string compare operator = and !=
#
STR1="Hello"
STR2="Hello"
if [ ${STR1} = ${STR2} ]
then
echo "Strings match"
else
echo "Strings don't match"
fiExample output:
Brief:
A simple script to show usage of string compare operator -z and -n
Source Code:
#!/bin/bash
#
# Author : Emertxe (https://www.emertxe.com)
# Date : Tue 16 Feb 2016 16:27:07 IST
# File : ls_008_02_ch6_stings.sh
# Title : Operators - String Compare
# Description : A simple script to show usage of string compare operator -z and -n
#
STR1="Hello"
STR2="Hello"
if [ -z "${STR1}" ]
then
echo "String1 is empty"
else
echo "String1 is NOT empty"
fi
echo ":$STR:"
if [ -n "${STR2}" ]
then
echo "String2 is NOT empty"
else
echo "String2 is empty"
fiExample output:
Brief:
A simple script to show usage of logical operators
Source Code:
#!/bin/bash
#
# Author : Emertxe (https://www.emertxe.com)
# Date : Tue 16 Feb 2016 16:27:07 IST
# File : ls_009_ch6_logical_operators.sh
# Title : Operators - Logical
# Description : A simple script to show usage of logical operators
#
echo -n "Enter a NUM: "
read NUM
# Check whether a number is between 10 and 20 (Using AND -a operator)
if [ $NUM -ge 10 -a $NUM -le 20 ]
then
echo "$NUM is between 10 and 20"
else
echo "$NUM is NOT between 10 and 20"
fi
echo -n "Enter another NUM: "
read NUM
# Check whether a number is between 10 and 20 (Using OR -o operator)
if [ $NUM -lt 10 -o $NUM -gt 20 ]
then
echo "$NUM is NOT between 10 and 20"
else
echo "$NUM is between 10 and 20"
fiExample output:
Brief:
A simple script to show usage while loop
Source Code:
#!/bin/bash
#
# Author : Emertxe (https://www.emertxe.com)
# Date : Tue 16 Feb 2016 16:27:07 IST
# File : ls_010_01_ch6_while_loop.sh
# Title : Loops - while
# Description : A simple script to show usage while loop
#
COUNT=0
while [ $COUNT -lt 5 ]
do
echo "Loop count is ${COUNT}"
COUNT=$((COUNT + 1))
done
echo "Done"Example output:
Brief:
Sum of N natural numbers using while loop
Source Code:
#!/bin/bash
#
# Author : Emertxe (https://www.emertxe.com)
# Date : Tue 16 Feb 2016 16:27:07 IST
# File : ls_010_02_ch6_while_loop.sh
# Title : Loops - while
# Description : Sum of N natural numbers using while loop
#
echo -n "Enter a number: "
read NUM
let SUM=0;
let I=1
while [ $I -le $NUM ]
do
SUM=`expr $SUM + $I`
I=$((${I} + 1))
done
echo "The sum of the first $NUM numbers is: $SUM"Example output:
Brief:
A simple script to demonstrate for loop [ Bash syntax ]
Source Code:
#!/bin/bash
#
# Author : Emertxe (https://www.emertxe.com)
# Date : Tue 16 Feb 2016 16:27:07 IST
# File : ls_011_01_ch6_for_loop.sh
# Title : Loops - for
# Description : A simple script to demonstarte for loop [ Bash syntax ]
#
COUNT=0
for i in 0 1 2 3 4
do
echo "Loop count is ${COUNT}"
COUNT=$((COUNT + 1))
doneExample output:
Brief:
A simple script to demonstrate for loop [ C syntax ]
Source Code:
#!/bin/bash
#
# Author : Emertxe (https://www.emertxe.com)
# Date : Tue 16 Feb 2016 16:27:07 IST
# File : ls_011_02_ch6_for_loop.sh
# Title : Loops - for
# Description : A simple script to demonstarte for loop [ C syntax ]
#
COUNT=0
for ((i = 0; i < 5; i++))
do
echo "Loop count is ${COUNT}"
COUNT=$((COUNT + 1))
doneExample output:
Brief:
Sum of N natural numbers using for loop
Source Code:
#!/bin/bash
#
# Author : Emertxe (https://www.emertxe.com)
# Date : Tue 16 Feb 2016 16:27:07 IST
# File : ls_011_03_ch6_for_loop.sh
# Title : Loops - for
# Description : Sum of N natural numbers using for loop
#
echo -n "Enter a number: "
read NUM
let SUM=0;
for I in `seq $NUM` # seq command provides a sequence of numbers from 0 to $NUM
do
SUM=`expr $SUM + $I`
I=$((${I} + 1))
done
echo "The sum of the first $NUM numbers is: $SUM" Example output:
Brief:
A script to show the usage of command line arguments, Here we access positional arguments using $1, $2 …
Source Code:
#!/bin/bash
#
# Author : Emertxe (https://www.emertxe.com)
# Date : Tue 16 Feb 2016 16:27:07 IST
# File : ls_012_01_ch6_cmd_line_agrs.sh
# Title : Command line arguments
# Description : A script to show the usage of command line arguments,
# Here we access positional arguments using $1, $2 ...
echo "Total no. of argument: $#"
echo "Program name: $0"
echo "1st argument: $1"
echo "2nd argument: $2"
echo "3rd argument: $3"
Example output:
Brief:
A script to show the usage of command line arguments, Here we access arguments by iterating over $@
Source Code:
#!/bin/bash
#
# Author : Emertxe (https://www.emertxe.com)
# Date : Tue 16 Feb 2016 16:27:07 IST
# File : ls_012_02_ch6_cmd_line_agrs.sh
# Title : Command line arguments
# Description : A script to show the usage of command line arguments, Here we access arguments by iterating over $@
#
echo "Total no. of argument: $#"
echo "Argument list: $@" # Commonly used
echo "Argument list: $*"
# Iterate over arguments ($@)
for ARG in $@
do
echo $ARG
done Example output:
Brief:
A script to show the usage of function
Source Code:
#!/bin/bash
#
# Author : Emertxe (https://www.emertxe.com)
# Date : Tue 16 Feb 2016 16:27:07 IST
# File : ls_013_01_ch6_function.sh
# Title : Functions
# Description : A script to show the usage of function
#
# Function definition
function print_hello()
{
echo "====="
echo "Hello"
echo "====="
}
# Call the function - print_hello
print_hello
#print_helloExample output:
Brief:
A script to show the usage of function and how to pass arguments
Source Code:
#!/bin/bash
#
# Author : Emertxe (https://www.emertxe.com)
# Date : Tue 16 Feb 2016 16:27:07 IST
# File : ls_013_02_ch6_function.sh
# Title : Functions - Arguments
# Description : A script to show the usage of function and how to pass arguments
#
# Function definition
function find_sum()
{
SUM=`expr $1 + $2`
echo $SUM
}
# Pass arguments 10 and 20 to find_sum function
find_sum 10 20
# Save the output of function in a variable
RESULT=`find_sum 100 200`
echo $RESULT Example output:
Brief:
A script to show the usage of function and how to pass arguments Inside function:
$# – Gives no. of arguments
$@ – Contains the arguments to function
Accessing function arguments is similar to accessing command line arguments
Source Code:
#!/bin/bash
#
# Author : Emertxe (https://www.emertxe.com)
# Date : Tue 16 Feb 2016 16:27:07 IST
# File : ls_013_03_ch6_function.sh
# Title : Functions - Arguments
# Description : A script to show the usage of function and how to pass arguments
# Inside function:
# $# - Gives no. of arguments
# $@ - Contains the arguments to function
# Accessing function arguments is similar to accessing command line arguments
#
# Function definition
function find_sum()
{
echo "Arg count: $#"
echo "Arg list: $@"
SUM=0
# Iterate over function arguments
for ARG in $@
do
SUM=`expr $ARG + $SUM`
done
echo $SUM
}
# Call find_sum with many arguments
find_sum 1 2 3 4 5
find_sum 10 20Example output:
Brief:
A script to show how to declare an array and access its element.
Source Code:
#!/bin/bash
#
# Author : Emertxe (https://www.emertxe.com)
# Date : Tue 16 Feb 2016 16:27:07 IST
# File : ls_014_01_ch6_array.sh
# Title : Array
# Description : A script to show how to declare an array and access its elements
#
# Declare an array
FRUITS=(apple mango banana orange)
# Print value of each element
echo "element 0: ${FRUITS[0]}"
echo "element 1: ${FRUITS[1]}"
echo "element 2: ${FRUITS[2]}"
echo "element 3: ${FRUITS[3]}"
# Print size / length of array
echo "Length: ${#FRUITS[@]}"
echo "Whole array: ${FRUITS[@]}"
echo "Whole array: ${FRUITS[*]}"
echo "Looping over array elements"
# Iterate over array elements
for ITEM in ${FRUITS[@]}
do
echo $ITEM
doneExample output:
Brief:
A script to store all cmd line arguments to a array and prints
Source Code:
#!/bin/bash
#
# Author : Emertxe (https://www.emertxe.com)
# Date : Tue 16 Feb 2016 16:27:07 IST
# File : ls_014_02_ch6_array.sh
# Title : Array
# Description : A script to store all cmd line arguments to a array and prints
#
ARG=($*)
echo ${ARG[0]}
echo ${ARG[1]}
echo ${ARG[2]}
echo ${ARG[3]}
echo ${ARG[4]}Example output:
Brief:
A script to demonstrate different types of array access
Source Code:
#!/bin/bash
#
# Author : Emertxe (https://www.emertxe.com)
# Date : Tue 16 Feb 2016 16:27:07 IST
# File : ls_014_03_ch6_array.sh
# Title : Array
# Description : A script to demonstrate different types of array access
#
array=(zero one two three four five)
# Element 0 1 2 3 4 5
echo ${array[0]} # zero
echo ${array:0} # zero, Parameter expansion of first element,+ starting at position # 0 (1st character).
echo ${array:1} # ero, Parameter expansion of first element, + starting at position # 1 (2nd character).
echo "--------------"
echo ${#array[0]} # 4, Length of first element of array.
echo ${#array} # 4, Length of first element of array. (Alternate notation)
echo ${#array[1]} # 3, Length of second element of array. Arrays in Bash have zero-based indexing.
echo ${#array[*]} # 6, Number of elements in array.
echo ${#array[@]} # 6, Number of elements in array.
echo "--------------"
# Quoting permits embedding whitespace within individual array elements.
array2=([0]="first element" [1]="second element" [3]="fourth element")
echo "The ${array2[0]}" # first element
echo "The ${array2[1]}" # second element
echo "The ${array2[2]}" # Skipped in initialization, and therefore null.
echo "The ${array2[3]}" # fourth element
echo "The lenght of ${array2[0]} ${#array2[0]}" # 13 (length of first element)
echo "The number of elements in the array ${#array2[*]}" # 3 (number of elements in array)
Example output:
Brief:
A script to demonstrate usage of sed command
Source Code:
#!/bin/bash
#
# Author : Emertxe (https://www.emertxe.com)
# Date : Tue 16 Feb 2016 16:27:07 IST
# File : ls_015_ch6_sed.sh
# Title : Command - sed
# Description : A script to demostrate usage of sed command
#
# Uses printf to color the pattern
echo "I am in GREEN" | sed ''/GREEN/s//`printf "33[32mGREEN33[0m"`/''Example output:
