LINUX Lessons

LINUX

Shell Scripts

Output Command

echo

Input command

read

read <variable name>

Ex: read a

read b

read a b

To create and execute a program

First open a file using ‘cat’ or ‘vi’ or any other editor, then in it give the program then save the file. Then give the execute permission to that file using ‘ch mod’. Then execute that program give ‘file name’ then Enter. Example (1) Write a program to clear the screen and display in the screen ‘UNIX programming’

$ vi f1

clear

echo UNIX programming

: wq (it is for save and quit from the ‘vi’ file)

$ chmod 777 f1

$ f1, enter

or $ sh f1

(2) Write a program to enter a number and display it on the screen.

clear

echo enter the number:

read n

echo the number is $n

Arithmetic Operators :-

There are 5 arithmetic operators they are ‘+’ for add, ‘-‘for subtract, ‘/’ for divide, ‘*’ for multiplied, ‘%’ for reminder of a division.

Write a program to find the sum of two entering number clear

echo enter the number:

read n

echo enter another number:

read m

s=’expr $ n + $ m’

echo the sum is: $ s

Write a program to find the multiplication of two entering numbers

clear

echo ENTER TWO NUMBERS:
read a b

S=’expv $ a “*” $ b’

echo THE PRODUCT IS: $ S

Conditional Statement - ‘IF’

Form of ‘if’ statement :-

a) if <condition>
then

statement

b) if <condition>

then

statements

else

statements

Relational operators

> (greater then) à -gt

>= (grater then or equal to) à -ge

< (less than) = -lt

<= (less than or equal to) = -le

= (equal to) = -eq

# (not equal to) = -ne

Example 1) if test $ a –qt $ b (if a>b)

Then

if test $ a –eq 0 (if a=0)

Then

1) Write shell script to input a number and check if it is positive of negative.

Clear

Echo enter the number

Read a

If text $ a –gt 0

Then

Echo Positive Number

Else

Echo Negative Number

:wq

2) Write a shell scrift input a number and check if it is even or odd.

VI F2

Clear

Echo Number

Read n

S = ‘expr $ n % 2

If text $ s –eq 0

Then

Echo Even Number

Else

Echo Odd Number

:wq

‘IF’ Condition

if ($ s –eq 0)

3) To input two number and to find the greater one.

Vi Greater

Clear

Echo INPUT A NUMBER:
read b

If [ $ a –gt $ b]

Then

Echo FIRST NUMBER IS GREATER THAN SECOND

Else

Echo SECOND NUMBER IS GRATER THAN FIRST.

Nested ‘if’ Statement

How to give

If <condition>

Then

If <condition>

Then

Statements

Else

If <condition>

Then

Statements

To input two number and find which one is greater or both are same or not.

Clear

Echo INPUT TWO NUMBERS;

Read a b

If [$ a –gt $ b]

Then

Echo FIRST NUMBER IS GREATER

Else

If [ $ b –gt $ a ]

Then

Echo SECOND NUMBER IS GREATER

Else

Echo BOTH ARE EQUAL

:wq

Write a program to find that the entering or inputing number is Positive, Negative, or Zero.

Clear

Echo ENTER A NUMBER

Read n

If [$ n –gt 0]

Then

Echo Positive number

Else

If [$ n –lt 0]

Then

Echo Negative Number

Else

Echo ZERO

: wq

4) To input an year and to check if it is a leap year or not.

Clear

Echo ENTER A YEAR

Read y

S = ‘ expr $ y % 4 ‘

If test $ s –eq 0

Then

Echo IT IS A LEAP YEAR

Else

Echo IT IS NOT A LEAP YEAR

:wq

5) Write a shell script to input a number and display the menu given below, then accept the choice of the user and display the result on the screen.

MENU

1. ADDITION

2. SUBTRACTION

3. DIVISION

4. MULTIPLICATION

Clear

Echo ENTER ANY SL.NO OF BELOW MENU

ECHO MENU

Echo1. ADDITION

Echo2. SUBTRACTION

Echo3. DIVISION

Echo4. MULTIPLICATION

Read n

If [$ n –eq 1]

Then

S = ‘expr $ a + $ b ‘

Echo THE RESULT IS: $ S

IF [$ N –EQ 2]

Then

S = ‘Expr $ a / $ b’

Echo THE RESULT IS: $ S

If [$ n –eq 4]

Then

S = ‘expr $ a “*” $ b’

Echo THE RESULT IS: $ S

:wq

Write the program to input the Name and Marks for 2 different subject Marks in 100 of the student calculate the total mark, percentage of mark and grade. The grade is calculated as follows

(a) If the percentage of mark is greater than 80 Grade ‘Distinction’

(b) If the percentage of mark is between 60 and 80 Grade ‘First class’

(c) If the percentage of mark is between 50 and 60 Grade ‘Second class’

(d) If the percentage of mark is between 30 and 50 Grade ‘Third class’

(e) If the percentage of mark is less than 30 Grade ‘Failed’

Clear

Echo ENTER YOUR NAME:

Read a

Echo ENTER THE MARKS OF TWO SUBJECT:

Read b c

S = ‘expr $ b + $ c.’

S = ‘expr $ S / 2’

Echo THE TOTAL MARK IS: $ S

Echo PERCENTAGE OF MARK IS: $ P

If [ $p –ge 80]

Then

Echo DISTINCTION

Else

If [$P –ge 60]

Then

Echo FIRST CLASS

Else

If [$ P –ge 50]

Then

Echo SECOND CLASS

Else

If [$ P –ge 30]

Then

Echo THIRD CLASS

Else

If [$ P –it 30]

Then

Echo FAILED

:WQ

Looping Statements

Statements which are used to execute commands repeatedly for a specific number of lines.

(1) While

(2) Until

While

How to give

While [Condition]

Statements

Done

1. C=1

While [$ C –le 10]

Do echo Hello

Done

Display ‘Hello’ infinity until we press ‘Del’ key because ‘value of C’ is not increasing it will always one and it is less than 10.

2. C=1

While [$ c –le 10]

Echo $ C

C = ‘expr $ C + 1’

Done

:wq

Display 1 to 10 then come out

3. Write shell scift to print the serious 100, 98, 96,……….0.

Clear

A=100

While [$a –ge 0]

Echo $ C

C = ‘expr $ C -2’

Done

:wq

4. Write a shell script to input 10 number and to calculate their sum.

Clear

C=1

S=0

While [$ C –le 10]

Echo ENTER NUMBER:

Read a

S =’expr $ S a’

C = ‘expr $ C + 1’

Done echo SUM OF 10 NUMBERS IS: $ S

:wq

5. Input 10 number. Calculate the average.

Clear

C=1

S=0

While [$C –le 10]

Do echo ENTER NUMBER:

Read a

S = ‘expr $ S + $ a’

C= ‘expr $ C + 1’

Done

F=’expr $ S / 10’

Echo AVERAGE OF TEN NUMBERS IS: $ F

:wq

6. To input 10 numbers and to count the number of Positive numbers, negative numbers and zeros.

Clear

C=1

R=0

S=0

T=0

While [$C –le 10]

Do echo ENTER NUMBER:

Read a

If [$ a –gt 0]

Then

R=’expr $ R + 1’

If [$ a –it 0]

Then

S=’expr $ S + 1’

If [$ a –eq 0]

Then

T=’expr $ + 1]

C=’expr $ C + 1’

Done

Echo NUMBER OF POSITIVE NUMBER IS: $ R

Echo NUMBER OF NEGATIVE NUMBER IS: $ S

Echo ENTER OF ZERO IS: $ T

:wq

6) Input 10 numbers calculate the sum of positive numbers and negative numbers saperately and number of zero’s input.

Clear

C=1

R=0

S=0

T=0

While [$C –le 10]

Do echo ENTER NUMBER:

Read a

If [$ a –gt 0]

Then r=’expr $a + $r’

Else

If [$a –lt 0]

Then

S= ‘expr $ a + $ s’

Else

T=’expr $ a + 1’

C = ‘expr $ c + 1’

Done

Echo THE TOTAL OF POSITIVE NUMBERS IS: $ r

Echo THE TOTAL OF NEGATIVE NUMBERS IS: $ s

Echo THE TOTAL ZERO: $ t

:wq

7) Input 10 numbers and find the highest number.

Clear

Echo INPUT THE FIRST NUMBER:

Read n

High = $ n

Echo INPUT THE OTHER NUMBER:

C=1

While [$C –le 9]

Read n

If [$ n –gt $ high]

Then

High = $ n

C=’expr $ c + 1’

Done

Echo HIGHEST NUMBER IS: $ high

8) Input 10 numbers and find the highest and the smallest.

Clear

Echo ENTER A NUMBER:

Read n

High = $ a

Low + $ a

Echo ENTER OTHER NUMBER:

C = 1

While [$ c –le 9]

Read a

If [$ a –gt $ high]

Then

High = $ n

If [$ a –it $ low]

Then

Low = $ a

C = ‘expr $ c + 1’

Done

Echo highest is: $ high

Echo SMALLEST IS: $ low

:wq

To copy a file from one login (Cu01) to (Cu02) second login

Cp / usr/student +/Cu01/VINOD.

That is file ‘VINOD’ is copy to CU02. First give the copy command that is ‘cp’ then space the give the correct path that is ‘/usr/student/Cu01/VINOD ‘ with file name, then space, then’dot’ that is ‘.’

How to give

Cp <path>.

That is path= /usr/student/Cu01/VINDO

‘Break’ and ‘continue’ commands

which is used in looping statements

Break command

While [condition]

Statements

Break

Done

Note;- ‘Break’ will stop at where we enter

Example 1)

C=1

While [$ c –le 10]

Echo NUMBER

Read n

If [$n –lt 0]

Then

Echo ONLY POSITIVE NUMBERS

Break

C= ‘expr $ c + 1’

Done

‘Continue’ command

It will cancel the current execution of the loop and starts it once again

How to give

While [condition]

Statements

Continue

Done

Example 1)

C=1

While [$ c –le 10]

Do echo NUMBER

Read n

If [$ n –lt 0]

Then

Echo ONLY POSITIVE NUMBERS

Continue

C=’expr $ c + 1 ‘

Done

1) Write a shell scrift to input 10 numbers between 50 and 100, if any other number is input it should give an error message and stop the execution.

Clear

C=1

While [$ c –le 10]

Echo NUMBERS ONLY BETWEEN 50 AND 100

Break

Fi c=’expr $ c +1’

Done

:wq

And -> -a, &&

OR -> -o, | |

When the program execute any error come and how we can exit from the program

Press ‘ctrl’ + ‘.’ ‘Delete’, ‘Delete’ key press.

UNIX Division

In UNIX when we divide any number its answer we get only the part that is we cannot get any decimal. Decimal is don’t accept the ‘UNIX’

That is, If S=15, r=2, then m=’expr $ S /$ r’

Echo $ m , will be ‘r’ but the correct answer is ‘7.5’. So we want to care when we divide.

‘/C’ with ‘echo’ command

Slash ‘c’ option given with echo command will display the message and then cursor will wait on the same line.

How to give

I) echo <message> “/c”

while [condition]

………………….

Echo “$ a \ c “

II) Echo “ $ a \ C “

Note:- In ‘I’ we can give message also with the answer, but in ‘II’ we get answer only in the same line. That is in ‘I’ THE SUM IS: 21 but in ‘II’ 21.

In ‘I’ we give the first echo that is echo with message, is give before the ‘while’. Then at the answer part give second ‘echo’ with variable name. But in ‘II’ give ‘echo’ at the answer part.

‘And’ and ‘or’ in while condition or give two condition together.

And -> ‘-a’, ‘&&’

Or -> ‘-o’, ‘||’

It is for give two condition in the ‘while’statements. That is

While [$ a –gt 10 && $ a –lt 15]

While [$ a –gt 10 –a $ a –lt 15]

That is number between 10 and 15. But in ‘OR’

While [$ b –gt 50 $ b –gt 100]

While [$ b –gt 50 | | $ b –gt 100]

That is number is less than 50 or greater than 100 only.

How to give

‘And’

While [condition –a condition]

While [condition && condition]

‘Or’

While [condition -0 condition]

While [condition | | condition]

1) Write a shell script to input 10 odd numbers. If an even number is input it should display an error message and start the execution once again.

Clear

C = 1

While [$ c –le 10]

Echo NUMBER INPUT:

Read n

S = ‘expr $ n % 2 ‘

If [$ s –eq 0]

Then

Echo ERROR!!! INPUT ODD NUMBERS ONLY.

Continue

C = ‘expr $ c + 1’

Done

;WQ

2) Write a shell script to input a number and to calculate its factorial

That is if we input 5, factorial is: 5x4x3x2x1=120

Clear

F =1

Echo ENTER A NUMBER

Read n

While [$ n –ge 1]

F = ‘expr $ f “*” $ n ‘

N = ‘expr $ n – 1 ‘

Done

Echo FACTORIAL IS: $ f

:wq

3) Input the value, then revenue the value and display on the screen? That is 102 as 201.

Clear

Echo NUMBER:

Read n

While [$ n –gt 0]

R = ‘expr $ n % 10 ‘

Echo “$ r \ c “

N = ‘expr $ n / 10’

Done

:wq

4) Input the value of ‘x’ and ‘y’ and find the ‘xy’. That is x=2, y=3, 2x2x2=8

Clear

F=1

Echo INPUT THE NUMBER:

Read x

Echo INPUT HOW MUCH TIME NUMBER SHOULD MULTIPLIE:

Read y

While [$ y –gt 0]

F=’expr $ S “*” $ f ‘

Y= ‘expr $ y – 1’

Done

Echo THEN GET: $ f

:wq

5) A shell script to input a number and calculated the sum of its digits. That is 2893=2+8+9+3=21

Clear

S=0

Echo NUMBER:

Read n

Echo SUM IS: “\C”

While [$ n –gt 0]

R=’expr $ n % 10’

S= ‘expr $ s + $ r ‘

N= ‘expr $ n / 10’

Done echo $ S

:wq

UNTIL

Until [condition]

Statements

Done

In until the condition is false it will continue, but when the condition give become true it will stop the looping. But in while when the condition is true it will do, but condition become false it will stop looping. So ‘Until’ is just opposite of ‘while’.

C=1

Until [$ C –gt 0]

Echo $ C

C = ‘expr $ C + 1’

Done

1) Write a shell script to print the series 100, 98,96,…..0 using ‘Until’.

C=100

Until [$ c –lt 0]

Echo $ C

C= ‘expr $ C – 2’

Done

:WQ

‘FOR’ Statement.

For ,<Variable name> in <list>

Statements

Done

‘For’, it is used for list more than one items. At the list place we can give list of items, then we execute this we can get one by one will list at the screen. We cannot give any condition at the ‘list’ place. But at ‘statements’ we can give.

S=0

For x in 10 20 30 40 50

S= ‘expr $ S + $ x

Done

Echo $ S

Note:- Answer will be 150.

1) Assume that there are three files A1,A2,A3 in the disk. Write a shell script to display the contents of these files.

Clear

For x in A1,A2,A3.

Cat $x

Done

:Wq

2) Write a shell script to input two file names change the name of the file to the second file.

Clear

Echo ENTER THE OLD NAME AND NEW FILE NAME:

Read a b

Mv $ a $ b

3) Write a shell script to input three file name. The copy the contents of first two files to the third file and we can see it on the screen also.

Clear

Echo ENTER A NEW FILE NAME:

Read a

Echo ENTER TWO EXISTING FILE NAMES:

Read b c

Cat $ b $ C > $ a

Cat $ a

:wq

How we can give number to the lines in the file.

: Set nu

: Set number

To remove the line number from the file

: set nonu

: set no number

Copy one file to another file

(1) $ Cat file A > file B

(2) $ Cat file x file y > file z

(3) $ Cat file R file S >> file T

(1) It is to copy the contents of File A to the ‘File B’. (2) It is to copy the contents of two file that is ‘File X’ and ‘File Y’ to the another file ‘File Z’. (3) It is to copy the contents of two file but the another file also have the contents that is in the three files there is contents. This command will give the contents of ‘File T’, ‘File R’ and ‘File S’ in the file ‘File T’. That is it will oppend the file.

File checking

-r <file name>To check the read permission

-w <file name>To check the write permission

-x <file name>To check the executable permission

-f <file name> To check the file is exist and is an ordinary file

-d <file name> To check if it is a directory.

If [-r $ f] It is to check that the file in the variable ‘f’ have read permission

If [-w $ f] It is to check that the file in the variable ‘f’ have write permission

If [-x $ f] It is to check that the file in the variable ‘f’ have execute permission

If [-f $ f] It is to check that the file in the variable ‘f’ is exist or not

If [-d $ f] It is to check that the name in the variable ‘f’ is a directory or not.

1) Write a shell script to input a file name and to check its permissions.

Clear

Echo ENTER THE FILE NAME

Read h

If [-f $ h]

Then

If [-r $ h]

Then

Echo IT HAS READ PERMISSION

Else

Echo IT HAS NO READ

If [-w $ h]

Then

Echo IT HAS WRITE PERMISSION

Else

Echo IT HAS NO WRITE

If [-x $ h]

Then

Echo IT HAS EXECUTE PERMISSION

Else

Echo IT HAS NO EXECUTE PERMISSION

Else

Echo NO SUCH FILE

:wq

2) Write a shell script to input a file name check if it is a directory or and ordinary file. If it is a directory display the contents of the directory, if it is a file display the contents of the file.

Clear

Echo FILE NAME

Read r

If [-d $ r]

Then

Ls $ r

Else

If [-f $ r]

Then

Cat $ r

:Wq

3) Write a shell script to print a first ‘n’ number of the Fibonacci serious. We input the number ‘n’ then we get the list of that number. That is 0,1,2,3,5,8,…..

Clear

A=0

B=1

Echo ENTER THE NUMBER

Read n

Clear

Echo $ a

Echo $ b

C=2

While [$ c –lt $ n]

S=’expr $ a + $ b ‘

Echo $ S

A=$ b

B=$ s

C=’expr $ c + 1’

Done

:wq

4) Write a shell script to copy two file’s contents to an another existing file that is file have to contents and it can be see on the screen also.

Clear

Echo ENTER FILE NAME:

Read a

Echo ENTER ANOTHER TWO FILE:

Read b c

Cat $ b $ c >> $ a

Cat $ a

:wq

Command Line Arguments

It is values which are given in the command line along with the file name. At a time we can give ‘nine’ command line arguments [by default]. The first command line argument will be stored in the variable $ 1, $ 0 stores the file name or program file’s name.

$1) First command line argument.

$2) Second command line argument.

$3) Third command line argument.

$4) Forth command line argument.

$5) Fifth command line argument.

$6) Sixth command line argument.

$7) Seventh command line argument.

$8) Eight command line argument.

$9) Ninth command line argument.

$0) Name of the program file.

Vi F1

Clear

Echo $ 1

:wq

$ Ch mod 777 F1

$ F1 AAA

AAA it will display on the screen.

1) Write a shell script to find the sum of two numbers, using command line argument.

Vi LESH
clear

S= ‘expr $ 1 + $ 2’

Echo SUM IS : $ S

:wq

$ Ch mod 777 F1

$ LESH 100 50

SUM IS: 150. It will display on the screen.

2) Write a shell script to display the contents of a file given as command line argument.

Clear

Cat $ 1

Command line Arguments.

$ 0 Name of the program file

$ # Number of command line Arguments.

$ * List of command line Arguments.

Vi VINU

Clear

Echo THE NAME OF THE PROGRAM IS: $0

Echo THERE ARE 4 3 COMMAND LINE ARGUMENTS

ECHO the command line arguments are 4 8

:Wq

$ Ch mod 777 VINU

$ VINU 1 2 3 4 5 6

ANSWER ON THE SCREEN

THE NAME OF THE PROGRAM IS: VINU

THERE ARE 6 COMMAND LINE ARGUMENTS

THE COMMAND LINE ARGUMENTS ARE 1 2 3 4 5 6

3) Write a shell script to copy the contents of one file to another file and remove the first file. [The file names are given like command line arguments]

Vi VINOD

Clear

Cp $ 1 $ 2

Rm $ 1

:wq

$ Ch mod 777 VINOD

$ VINOD a b c d

4) Write a shell script to calculate and display the sum of the number given as command line arguments.

Clear

S=0

For x in $ *

S=’expr $ S + $ x’

Done

Echo $ S

:wq

5) Write a shell script to calculate the length of string.

Clear

Echo ENTER THE STRING:

Read S

A=’echo $ S | wc –c’

A=’expr $ a -1’

Echo $ a

:wq

String Comparisons

If we want to compare the two string are equal, we give like this:

If [$ a = $ b]

If we want to known the two strings are not equal, we give like this:

If [$ a ! = b]

String:- It is a group of character.

1) Input a string then find the length of the string and reverse the string.

Clear

Echo INPUT STRING

Read s

L= ‘expr $ s | wc –c ‘

L = ‘expr $ l -1’

Echo $ l

While [$ l –ge 1]

X= ‘echo $ S | Cut –c $ l’

Echo “$ x \ C”

L=’expr $ l – 1’

Done

:wq

Grep

It will display the lines in which the word is grep is used to find the words.

Grep “pattern” <file name>

Example grep “ manager” LESH:- It will display all lines in which the word ‘manager’ is found in the file ‘LESH’.

1) Input a string and a character in that string. Then print the position of occurance of that character in the string.

Clear

Echo ENTER A STRING

Read S

L=’echo 4 S | wc –c’

L=’expr $ l – 1 ‘

Echo ENTER A CHARACTER IN THE STRING

READ H

C=1

WHILE [$ C –LE $ L]

X=’ECHO $ S | cut –c $ c’

If [$ x = $ h]

Then

Echo POSITION IS: $ C

C= ‘expr $ C + 1’

Done

:wq

2) A shell script to input a string and a character in that string. Then display its position of the first occurance of the character in the string.

Clear

Echo ENTER A STRING

Read s

L=’echo $ S | Wc –C’

L=’expr $ l – 1 ‘

Echo ENTER A CHARACTER IN THE STRING

Read h

C=1

While [$ C –le $ l]

X=’echo $ S | Cut –C $ C ‘

If [$ x = $ h]

Then

Echo POSITION IS: $ C

Break

C=’expr $ C + 1’

Done

:wq.

HOME

<<PREVIOUS

Want Easy lessons and exercises!! Then search here:

Home