OS Practicals

for study VI editer

http://cc.iiti.ac.in/vicom.pdf

http://www.tutorialspoint.com/unix/pdf/unix-vi-editor.pdf

Practical List:

1. Study of Basic commands of Linux/UNIX.

2. Study of Advance commands and filters of Linux/UNIX.

3. Write a shell script to generate marksheet of a student. Take 3 subjects, calculate and display total marks, percentage and Class obtained by the student.

http://www.dailyfreecode.com/code/shell-script-generating-mark-sheet-1705.aspx

echo "Enter the five subject marks for the student"

read m1 m2 m3 m4 m5

sum1=`expr $m1 + $m2 + $m3 + $m4 + $m5`

echo "Sum of 5 subjects are: " $sum1

per=`expr $sum1 / 5`

echo " Percentage: " $per

if [ $per -ge 60 ]

then

echo "You get Distinction”

elif [ $per -ge 50 ]

then

echo “You get First class”

elif [ $per -ge  40 ]

then

echo "You get Second class"

else

     echo "You get Fail"

fi

OUTPUT

**********

     [04mca58@LINTEL 04mca58]$ sh filemenu.sh

     Enter the five subject marks for the student

     45

     35

     30

     40

     42   

     Sum of 5 subjects are: 192

     Percentage : 76.8

You get Distinction

4. Write a shell script to find factorial of given number n.

http://www.dailyfreecode.com/code/calculate-factorial-number-1533.aspx

echo "Total no of factorial wants"

read fact

ans=1

counter=0

while [ $fact -ne $counter ]

do

        counter=`expr $counter + 1`

        ans=`expr $ans \* $counter`

done

echo "Total of factorial is $ans"

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

output

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

Total no of factorial wants

5

Total of factorial is 120

5. Write a shell script which will accept a number b and display first n prime numbers as output.

http://www.bashguru.com/2009/11/shell-script-to-find-prime-number.html

#!/bin/bash

# SCRIPT: prime1.sh

# USAGE : ./prime1.sh

# PURPOSE: Finds whether given number is prime or not

#####################################################################



echo -n "Enter a number: "

read num

i=2



while [ $i -lt $num ]

do

  if [ `expr $num % $i` -eq 0 ]

  then

      echo "$num is not a prime number"

      echo "Since it is divisible by $i"

      exit

  fi

  i=`expr $i + 1`

done



echo "$num is a prime number "

Output:

[root@venu ]# ./prime1.sh

Enter a number: 1879

1879 is a prime number

[root@venu ]# ./prime1.sh

Enter a number: 119

119 is not a prime number

Since it is divisible by 7

6. Write a shell script which will generate first n fibonnacci numbers like: 1, 1, 2, 3, 5, 13,…

http://www.bashguru.com/2010/12/shell-script-to-generate-fibonacci.html



if [ $# -eq 1 ]

then

    Num=$1

else

    echo -n "Enter a Number :"

    read Num

fi



f1=0

f2=1



echo "The Fibonacci sequence for the number $Num is : "



for (( i=0;i<=Num;i++ ))

do

     echo -n "$f1 "

     fn=$((f1+f2))

     f1=$f2

     f2=$fn

done



echo

OUTPUT:

# sh fibo_iterative.sh 18

The Fibonacci sequence for the number 18 is : 

0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987 1597 2584 

# sh fibo_iterative.sh

Enter a Number :20

The Fibonacci sequence for the number 20 is : 

0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987 1597 2584 4181 6765

7. Write a menu driven shell script which will print the following menu and execute the given task.

 MENU

a.      . Display calendar of current month

b.      . Display today’s date and time

c.       . Display usernames those are currently logged in the system 

d.      . Display your name at given x, y position 

e.      . Display your terminal number

f.        . Exit

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

Echo “ MENU

a.      . Display calendar of current month

b.      . Display today’s date and time

c.       . Display usernames those are currently logged in the system 

d.      . Display your name at given x, y position 

e.      . Display your terminal number

f.        . Exit

“

Read i

Case “$i” in

1)      Cal ;;

2)         ;;

3)      ;;

4)      Tput cup 10 10

Echo pradish ;;

5)      Pwd ;;

6)      Exit ;;

*) echo “enter valid in put” ;;

esac

8. Write a shell script to read n numbers as command arguments and sort them in descending order.

echo $0  # script file name

echo $1  # first argument

echo $2  # second argument

echo $3  # third argument

9. Write a shell script to display all executable files, directories and zero sized files from current directory.

find $dir -size 0

DU ---- for dir

10. Write a shell script to check entered string is palindrome or not.

clear

echo "Ente

r a string to be entered:"

read str

echo

len=`echo $str | wc -c`

len=`expr $len - 1`

i=1

j=`expr $len / 2`

while test $i -le $j

do

k=`echo $str | cut -c $i`

l=`echo $str | cut -c $len`

if test $k != $l

then

echo "String is not palindrome"

exit

fi

i=`expr $i + 1`

len=`expr $len - 1`

done

echo "String is palindrome"

11. Shell programming using filters (including grep, egrep, fgrep)

Differences between grep, fgrep, egrep...

13 Jul, 2009  Tutorials

Grep is a very useful tool in the Unix world. If you don't know it already, it is very much like a search tool. It can search for a text or pattern in one or multiple input files or data coming from (unix) pipes.

Most of the Linux distributions out there offer three ways to use Grep from the command-line (aka terminal): grep, fgrep, and egrep.

grep

The grep command is the most common one but also the oldest. It offersBasic Regular Expression matching.
The particularity of BRE is that some metacharacters ({, }, and parenthesis) need to be escaped (using a backslash \) to be used properly. (see also egrepbelow)

grep 'testi\{1,2\}ng' file.txt

will match any lines containing either testing or testiing in file.txt.

fgrep

fgrep, short for fixed(-size strings) grep, is used to do a search for a string with a fixed size (can be seen as a constant), contrarely to patterns.

fgrep '{test}match*' file.txt

will match any text containing exactly {test}match*. No parsing or interpreting of regular expression or whatever, is done by grep.

egrep

egrep, short for extended grep, (contrarely to the simple grep) search for matches using a pattern written using Extended Regular Expressions. The changes from BRE is that you do not need to escape metacharacters, and also ERE provides three more metacharacters: |, +, and ? (note that they can still be used in the basic grep by escaping them).

egrep 'testi\{1,2\}ngs?' file.txt

will match any text containing any of: testing, testings, testiing, testiings.

10. Write a shell script to check entered string is palindrome or not.

clear

echo "Enter a string to be entered:"

read str

echo

len=`echo $str | wc -c`

len=`expr $len - 1`

i=1

j=`expr $len / 2`

while test $i -le $j

do

k=`echo $str | cut -c $i`

l=`echo $str | cut -c $len`

if test $k != $l

then

echo "String is not palindrome"

exit

fi

i=`expr $i + 1`

len=`expr $len - 1`

done

echo "String is palindrome"

12. Study of Unix Shell and Environment Variables.

Environment Variables:

Following is the partial list of important environment variables. These variables would be set and accessed as mentioned above:

Variable	Description
DISPLAY	Contains the identifier for the display that X11 programs should use by default.
HOME	Indicates the home directory of the current user: the default argument for the cd built-in command.
IFS	Indicates the Internal Field Separator that is used by the parser for word splitting after expansion.
LANG	LANG expands to the default system locale; LC_ALL can be used to override this. For example, if its value is pt_BR, then the language is set to (Brazilian) Portuguese and the locale to Brazil.
LD_LIBRARY_PATH	On many Unix systems with a dynamic linker, contains a colon-separated list of directories that the dynamic linker should search for shared objects when building a process image after exec, before searching in any other directories.
PATH	Indicates search path for commands. It is a colon-separated list of directories in which the shell looks for commands.
PWD	Indicates the current working directory as set by the cd command.
RANDOM	Generates a random integer between 0 and 32,767 each time it is referenced.
SHLVL	Increments by one each time an instance of bash is started. This variable is useful for determining whether the built-in exit command ends the current session.
TERM	Refers to the display type
TZ	Refers to Time zone. It can take values like GMT, AST, etc.
UID	Expands to the numeric user ID of the current user, initialized at shell startup.

13. Write a shell script to validate the entered date. (eg. Date format is : dd-mm-yyyy)

 #!/bin/bash
# Shell program to find the validity of a given date

dd=0
mm=0
yy=0

# store number of days in a month
days=0

# get day, month and year
echo -n "Enter day (dd) : "
read dd

echo -n "Enter month (mm) : "
read mm

echo -n "Enter year (yyyy) : "
read yy

# if month is negative (<0) or greater than 12
# then it is invalid month
if [ $mm -le 0 -o $mm -gt 12 ];
then
    echo "$mm is invalid month."
    exit 1
fi

# Find out number of days in given month
case $mm in
    1) days=31;;
    2) days=28 ;;
    3) days=31 ;;
    4) days=30 ;;
    5) days=31 ;;
    6) days=30 ;;
    7) days=31 ;;
    8) days=31 ;;
    9) days=30 ;;
    10) days=31 ;;
    11) days=30 ;;
    12) days=31 ;;
    *) days=-1;;
esac

# find out if it is a leap year or not

if [ $mm -eq 2 ]; # if it is feb month then only check of leap year
then
 if [ $((yy % 4)) -ne 0 ] ; then
    : #  not a leap year : means do nothing and use old value of days
 elif [ $((yy % 400)) -eq 0 ] ; then
    # yes, it's a leap year
    days=29
 elif [ $((yy % 100)) -eq 0 ] ; then
    : # not a leap year do nothing and use old value of days
 else
    # it is a leap year
    days=29
 fi
fi

# if day is negative (<0) and if day is more than
# that months days then day is invaild
if [ $dd -le 0 -o $dd -gt $days ];
then
    echo "$dd day is invalid"
    exit 3
fi

# if no error that means date dd/mm/yyyy is valid one
echo "$dd/$mm/$yy is a vaild date"

14. Write an awk program using function, which convert  each word in a given text into capital.

$ cat > test_lower_case
hi you are using awk script

$ cat < test_lower_case
hi you are using awk script

$ awk '{print toupper ($0) }' test_lower_case > test_uper_case

$ cat < test_uper_case
HI YOU ARE USING AWK SCRIPT

$

15. Write a program for process creation using C. (Use of gcc compiler). 

/* ----------------------------------------------------------------- */
/* PROGRAM  fork-01.c                                                */
/*    This program illustrates the use of fork() and getpid() system */
/* calls.  Note that write() is used instead of printf() since the   */
/* latter is buffered while the former is not.                       */
/* ----------------------------------------------------------------- */

#include  <stdio.h>
#include  <string.h>
#include  <process.h>
#include  <sys/types.h>

#define   MAX_COUNT  200
#define   BUF_SIZE   100

void  main(void)
{
   pid_t  pid;
     int    i;
     char   buf[BUF_SIZE];

     fork();
     pid = getpid();
     for (i = 1; i <= MAX_COUNT; i++) {
          sprintf(buf, "This line is from pid %d, value = %d\n", pid, i);
          write(1, buf, strlen(buf));
     } 

}