Oracle Applications: UNIX Commands

# -->system administrator prompt

$ -->user working prompt

Basic commands

1. logname -it displays the current user name

2. $pwd --it displays current working directory

3 $clear --it clear the screen

4. $exit – to logout from current user

5. $date – it displays system date and time

Sat mar 4 04:40:10 IST 2005

6. $ who am I – it displays current user name, terminal number, date and time at which

You logged into the system

Tecno ty01 mar 4 09:30

7. $who –To displays the information about all the users who have logged into the system

currently. Ie., each user login name, terminal number, date and time when the

person logged in

tecno1 tty01 mar 4 09:30

tecno2 tty05 mar 4 10:10

tecno3 tty06 mar 4 10:15

ie. Tecno1 – logname

tty01 - terminal name

mar 4 - date

09:30 -time

8. $finger – it displays complete information about all the users who are logged in

9. $cal – it displays previous month, current month and next month calendar

10. $cal year – it displays the given year calendar

Eg: $cal 2005 --it takes year from 1 t0 9999

11. $cal month year – it displays the given month calendar only

12. #init --to change system run levels

i. #init 0 -to shutdown the system

ii. #init 1 – to bring the system to single user mode

iii. #init 2 –to bring the system to multi user mode with no resource shared.

iv. #init 3 –to bring the system multi user mode with resource shared

v. #init 6 – halt and reboot the system to the default run level.

13. $banner “Bayon” – it prints a message in large letters

Creating files

There are two commands to create files 1. touch and cat

1. touch filename - it creates zero byte file size

Eg: $ touch sample

The size of sample file is zero bytes. Touch does not allow you store anything in a file. It is used for to create several empty files quickly.

Eg: $ touch file1 file2 file3 file4 file5

2. cat command

Syntax

i. $ cat >filename

e.g: $cat >sample

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

Ctrl+d (to close a file)

ii. $ cat >> sample --to append data to the file

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

Ctrl+d

iii. $cat file1 file2 file3 >file4

this would create file4 which contains contents of file1 followed by file2 and

followed by that of file3. ie., it concatenates file1, file2 and file3 contents and

redirects to file4. if file4 already contains something it would be over written.

3. $ cat <filename or $cat filename --to open a file

e.g: $cat sample --it displays sample file contents

e.g: $cat file1 file2 file3

-it displays file1 contents followed by file2 then followed by file3.

Removing files

4. rm command -to remove the given file

Syntax: $rm filename

$rm sample -it removes sample file

$rm –i filename -it asks confirmation before deleting the file.

$rm – sample

Remove sample? y –it removes

N – it wont remove

$rm file1 file2 file3 -it removes three files

$rm * -it removes all files in current directory

Creating directory

5. mkdir command -to make directory

Syntax: $mkdir directory name

e.g: mkdir tecno

creating multiple directories

$mkdir dir1 dir2 dir3 …dirn

Change directory

Syntax : $cd directory name

$cd tecnosoft

$pwd

/usr/tecno/tecnosoft

$cd .. –to change into parent directory

$cd\ -to change to root directory

Remove directory

1. $rmdir directory name -to delete a directory but directory should be empty

2. $rm –r directory name – it removes all files and sub directories, sub directory files

Including directory.

Shell Programs

write a prg to display list of files, the current working user’s list and present working directory.

Vi sp1

Ls –x

Who

Pwd

:wq (save and quit)

Execution of shell program:

Sh is the command to execute bourne shell programs

Eq: $sh sp1

$chmod 744 sp1

$sp1

Write program to display address

Vi sp2

Echo “ Patni Computer Systems”

Echo “Patni Knowledge park”

Echo “Navi Mumbai”

Echo “Phone :123456”

:wq (save and quit)

Write a prg count no. of users are currently logged into the system

Vi sp3

Echo “There are ‘who| wc – l’ users”

:wq (save and quit)

4. write a prg read name and display

Vi sp4

Echo “What is your name?”

Read name

Echo “hello $name”

:wq (save and quit)

Note: read is command to read variable value from the user. Read command reads value from keyboard upto space or enter key.

Eg 1: read a

Eg 2: read a b c

5. write a prg read two numbers and display

Vi sp5

Echo “entere 2 numbers:\c”

Read a b

Echo “your numbers are $a and $b

:wq (save and quit)

Operators

1. Arithmetic operators

Operator	Meaning
+	Addition
-	Subtraction
*	Multiplication
/	Division
%	Modulus Division

2. Relational operators

i. Numeric comparison operators

Operator	Meaning
-gt	Greate than
-ge	Greater than or equal to
-lt	Less than
-le	Less than or equal to
-eq	Equal to
-ne	Not equal to

ii. String comparison operators

Operator	Meaning
>	Greater than
<	Less than
=	Equal to
!=	Not equal to

3. Logical operators

Operator	Meaning
-a	Logical AND
-o	Logical OR
!	Logical NOT

6. Write a prg to read 2 numbers and display sum, difference, product and division

Vi sp6

Echo “Enter 2 numbers”

Read a b

C=’expr $a+$b’

Echo “a+b=$c”

C=’expr $a-$b’

Echo “a-b=$c”

C=’expr $a\*$b’

Echo “a*b=$a

C=’expr $a/$b’

Echo a/b=$c”

:wq (save and quit)

Note: expr is the command to evaluating arithmetic expressions. But expr is capable of carrying out only integer arithmetic

7. Write a prg to read 2 float numbers and display sum, difference, product and division

Vi sp7

Echo “Enter 2 float numbers”

Read a b

C=’echo $a+$b| bc’

Echo “a + b=$c”

C=’echo $a-$b|bc’

Echo “a-b=$c”

C=’echo $a\*$b|bc’

Echo “a*b=$a”

C=’echo $a/$b|c’

Echo “a/b=$c”

:wq (save and quit)

Control statements

There are 4 types of control instructions in shell. They are

i. sequence control instruction

ii. selection or decision control instruction

iii. repetition or loop control instruction

iv. case control instruction

The sequence control instruction ensures that the instructions are executed in the same order in which they appear in the program. Decision and case control instructions allow the computer to take a decision as to which instruction is to be executed next. The loop control instruction helps computer to execute a group of statements repeatedly.

Decision control statement

i. if – then – fi statement

syntax:

if control command

…....................

…………….

The if statement of unix is concerned with the exit status of a command. The exit status indicates whether the command was executed successfully or not. The exit status of a command is 0 if it has been executed successfully, 1 otherwise.

8. write prg to change directory

Vi sp8

Echo “Enter directory name”

Read dname

If cd $dname

Then

Echo “Changed to $dname”

Pwd

:wq (save and quit)

ii. if – then – else – fi statement

syntax:

if condition

then

----------

Else

-----------

The exit status of the control command is 0 then it executes then statements otherwise it executes else statements.

9. write a prg to copy a file

Vi sp9

Echo “Enter source filename and target file name

Read src trg

If cp $src $trg

Then

Echo “file copied successfully”

Else

Echo “Failed to copy the file”

10. write a prg to search string in a file

Vi sp10

Echo “Enter file name”

Read fname

Echo “Enter to string to search”

Read str

If grep $str $fname

Then

Echo “$str is found in the file $file”

Else

Echo “$str is not found in $fname”

:wq (save and quit)

11. write prg find greatest number of 2 numbers

Vi sp11

Echo “Enter two numbers”

Read a b

If [$a –gt $b] then

Echo $a is the greatest value

Else

Echo $b is the greatest value

:wq (save and quit)

12. Write a prg to check given no. is even or odd

Vi sp12

Echo Enter a number

Read n

If [‘expr $n%2 –eq 0]

Then

Echo $n is even number

Else echo $n is odd number

:wq (save and quit)

The Test command

If constructs depends upon whether of not the condition results into true or not. If constructs are generally used in conjuction with the test command. The test command helps us to find the contents of a variable, the number of variables and the type of file or kind of file permission. The test command returns an exit status after evaluating the condition.

Syntax:

If test condition

Then

Else

13. write a prg to check how many users working on the system

Vi sp13

Total=’who| wc –l’

If test $total –eq 1

Then

Echo “You are the only user working…”

Else

Echo “There are $total users working…”

:wq (save and quit)

14. Write a prg to check given number is +ve or –ve number

Vi sp14

Echo “enter a number”

Read num

If test $num –gt 0

Then

Echo “$num is +ve number”

Else

Echo “$num is –ve number”

:wq (save and quit)

15. write a prg to find student result

Vi sp15

Echo “Enter three subject marks:”

Read m1 m2, m3

If [$m1 –gt 40]

Then

If [$m2 –gt 40]

Then

If [m3 –gt 40]

Then

Echo “PASS”

Else

Echo “FAIL”

Else

Echo “FAIL”

Else

Echo “FAIL”

:wq (save and quit)

16. write a prg to print greeting

Vi sp16

Hour = ‘date|cut –c 12,13’

If [$hour –ge 0 –a $hour –le 11]

Then

Echo “Good Morning…”

Else

If [hour –ge 12 –a $hour –le 17]

Then

Echo “Good Afternoon…”

Else

Echo “Good Evening…”

:wq (save and quit)

File test commands

The test command has several options for checking the status of file

Option	Meaning
-s file	True if the file exists and has a size greater than 0
-f file	True if the file exists and is not a directory
-d file	True if the file exists and is directory file
-c file	True if the file exists and is character special file
-b file	True if the file exists and is a block special file
-r file	True if the file exists and you have a read permission to it
-d file	True if the file exists and you have a write permission to it
-x file	True if the file exists and you have a execute permission to it

17. write a prg to check for ordinary file and display it contents

Vi sp17

Echo “Enter a file name”

Read fname

If test –f $fname

Then

Cat $fname

Else

Echo “given file is not ordinary file”

:wq (save and quit)

iii. if – then – elif – fi statement

18. w a p to check given file is ordinary or directory file

Vi sp18

Echo “Enter a file name: “

Read fname

If [-f $fname]

Then

Cat $fname

Elif [-d $fname]

Then

Else

Echo $fname is not file and not a directory

:wq (save and quit)

19. write a prg to check read permission

Vi sp19

Echo “Enter a file name”

Read fname

If [-r $fname]

Cat $fname

Else

Chmod u+r $fname

Cat $fname

:wq (save and quit)

20. write a prg to append data to the file

Vi sp20

Echo “enter a filename”

Read $fname

If [-f $fname]

Then

If [-w $fname]

Then

Echo “Enter data to file to stop press ctrl+d…”

Cat >>$fname

Else

Chmod u+w $fname

Echo “enter data to file to stop press ctrl+d…”

Cat >>$fname

Else

Echo “Enter data to file to stop press ctrl+d…”

Cat >>$fname

:wq (save and quit)

String test commands

Condition	Meaning
String1 = String2	True if the strings are same
String1 != String2	True if the strings are different
-n String1	True if the length of string is greater than 0
-z string	True if the length of the string is zero

21. Write a prg to compare two strings

Vi sp21

Echo “Enter first string:”

Read str1

Echo “Enter second string:”

Read str2

If test $str1 = str2

Then

Echo “Both strings are equal”

Else

Echo “Strings are not equal”

:wq (save and quit)

22. Write a prg check given string is empty or not.

Vi sp22

Echo “Enter a string”

Read str

If [-z $str]

Then

Echo “String is empty”

Else

Echo “Given string is not empty”

:wq (save and quit)

iv. case – esac statement

syntax

case value in

choice 1)

----------

;;

Choice 2)

---------

;;

Choice n

--------

----------

;;

Esac

Firstly, the expression following the case key work is evaluated. The value the it yields is then matched, one by one against the potential choices (choice1, choice2 and choice 3 in the above form). When a match is found, the shell executes all commands in that case up to ;;. These pair of semicolons placed at the end of each choice are necessary.

23. Sample program for case

vi sp23

echo “enter a number b/n 1 to 4 “\c”

read num

case $num in

1) echo “you entered 1”

;;

2) echo “you entered 2”

;;

3) echo “you entered 3”

;;

4)echo “you entered 4”

;;

*) echo “invalid number. Enter number b/n 1 to 4 only”

;;

esac

: wq (save and quit)

24. Write a prg to check given character is upper case alphabe or lower case alphabet or digit or special character

Vi sp24

Echo “enter a single character”

Read ch

Case $ch in

[a-z] echo “you entered a small case alphabet”

;;

[A-Z] echo “you entered a upper case of alphabet”

;;

[0-9] echo “you entered a digit”

;;

?) echo “you entered a special character”

;;

*) echo “you entered more than one character”

;;

Esac

:wq (save and quit)

25. write a prg to display file contents of write on to file or execute based on user choice

Vi sp25

Echo “enter a file name:\c”

Read fname

Echo “Main menu”

Echo “-------------“

Echo “r.read mode”

Echo “w. write mode”

Echo “x.execute mode”

Echo “enter mode:\c”

Read mode

Case $mode in

if [-f $fname –a –r $fname] then

cat $fname

;;

if [-f $fname –a –w $fname] then

echo “Enter data to file at end press ctrl+d : “

cat >fname

;;

if [-f $fname –a –x$fname] then

chmode u+x $fname

$fname

;;

*) echo “you entered invalid mode …”

;;

Esac

:wq (save and quit)

26. write a menu driven prg which has following options:

i. contents of current directory

ii. list of users who have currently logged in

iii. present working directory

iv. calendar

v. exit

vi sp26

echo “main menu”

echo “----------“

echo “1. list of files”

echo “2. list of users”

echo “3. present working directory”

echo “4. display calendar”

echo “5. exit”

echo “enter your choice :\c”

read choice

case $choice in

1)ls –x

;;

2) who

;;

3) pwd

;;

4) echo “Enter month and year”

Read m y

Cal $m $y

;;

5) banner “Thank you”

Sleep 1

Exit 0 --to terminate execution of shell program

;;

*) echo “Choice is wrong try again!!!”

;;

Esac

:wq (save and quit)

Looping control statements

A loop involves repeating some portion of the program either a specified no of times of times or until a particular condition is being satisfied. There are three methods by way of which we can repeat a part of a program. There are

1. Using while statement

2. Using Until statement

3. Using a for statement

I) While statement

Syntax

While [condition]

-------

done

The statements within the while loop would keep on getting executed till the condition is true. When the condition is false, the control transfers to after done statement.

27. write a prg display numbers 1 to 10

vi sp27

echo “The numbers from 1 to 10 are:”

i=1

while [$i –le 10]

echo $i

i= ‘expr $i +1’

done

28. write a prg copy file from root to user directory

Vi sp28

Flag=1

while[$flag –eq 1]

Echo “enter a file name:\c”

Read fname

Cp $fname/usr/patni/$fname

Echo “$fname copied…”

Echo “do u wish to continue [1 –yes/0 –n0]:”

Read flag

Done

:wq (save and quit)

The break statement

When the key word break is encountered inside any loop, control automatically passes to the first statement after the loop

The continue statement

When the keyword continue is encountered inside any loop, control automatically passes to the beginning of the loop

29. write a prg display file contents if file existing

Vi sp29

X=0

While test $x=0

Echo “enter a file name:\c”

Read fname

If test! –f $fname

Then

Echo “$fname is not found…”

Continue

Else

Break

Done

Cat $fname|more

:wq (save and quit)

The until loop

Syntax:

Until [condition]

-------

Done

The statements within the until loop keep on getting executed till the condition is false. When the condition is true the control transfers to after done statement

30. write a prg print numbers 1 to10

vi sp30

i=1

until [$i – gt 10]

echo $i

i=’expr $i +1’

done

:wq (save and quit)

The True and False command

To execute the loop an infinite no. of times

31. Write sample prg for True command.

Vi sp31

While true

Clear

Banner “Hello”

Sleep 1

Clear

Banner “Bayon”

Sleep 1

Done

:wq (save and quit)

Note – The above prg executes continuous to stop execution press ctrl+break

32. write a prg for false command

Vi sp32

Until false

Clear

Banner “Hello”

Sleep 1

Clear

Banner “Bayon”

Sleep 1

Done

:wq (save and quit)

The Sleep command

The sleep command stops the execution of the program the specified no. of seconds.

The For loop

Syntax

For variable in value1 value2 value3…valuen

--------

Done

The for allows us to specify a list of values which the variable in the loop can take. The loop is then executed for each value mentioned in the list.

33. Write a program to demonstrate for loop

vi sp33

for I in 1 2 3 4 5

echo $i

done

:wq (save and quit)

34.

for i in Patni Computers system ltd.,

echo $i

done

:wq (save and quit)

35. write a prg to display all files in current directory

Vi 35

For I in *

If test –f $i –a –r $i

Then

Cat $i| more

Sleep 1

Clear

Done

:wq (save and quit)

36. write a prg to display all sub-directories in the current directory

Vi sp36

For I in *

If [-d $i]

Then

Echo $i

Done

:wq (save and quit)

Positional parameters

When the arguments are passed with the command line, shell puts each word on the command line into special variables. For this, the shell uses something called as ‘Positional parameters’. These can be thought of as variables defined by the shell. They are nine number, named $1 through $9

Consider the following statement, where sp37 is any executable shell script file and the remaining are the arguments. $sp37 Technosoft solutions is a computer training and development institute. On entering such command, each word is automatically stored serially in the positional parameters. Thus, #0 would be assigned sp37, s$1 would be assigned “Technosoft”, $2 “solutions”, $3 is “is” and so on, till institute “,” which is assigned to $9

37. write a prg to copy a file using positional parameters

Vi sp37

if cp $1 $2

then

echo “File copied successfully “

else

echo “Failed to copy”

:wq (save and quit)

$chmod 744 sp37

$sp37 a1 a2

In above command it passes a1 to $1 and a2 into $2, then it copies a1 contents to a2

S* - contains entire string of arguments

S# - contains the no. for arguments specified in the command.

% !! (recall last command)

% !-3 (recall third most recent command)

% !5 (recall 5th command in list)

% !grep (recall last command starting with grep)

% cp science.txt tempfile.txt

% ls (to check if it has created the file)
% rm tempfile.txt
% ls (to check if it has deleted the file)

Pages

Wednesday, November 30, 2011

UNIX Commands

# -->system administrator prompt

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