System Software LAB - Exercise 3

Exercise No : 3 grep, awk, sed

Aim :

To demonstrate the use of grep , awk and sed

Description:

1. Using grep command

Grep command used to filter the data. Example in the redhat.txt file it has the word rhel5. You can list out line with has the word rhel5. So the grep command is used for this purpose.

Shell Program
$ cat>god
god is great
god is present everywhere
[2]+ Stopped cat>god

Create a shell script with file name grep1.sh

echo “displaying a string from a file”
echo “get file name”
read s
echo “get string”
read i
grep $i $s

OUTPUT

$ grep.sh

displaying a string from a file
get file name
god
get string
great
god is great


2. Using awk command

cut and awk may both be used to select a specific field from the output of a command. A typical application would be to create a list of currently logged-in users:

Create a shell script with file name cut1.sh

#!/bin/sh
#
# using cut:
USERS=`who | cut -f1 -d" "`
echo "Users on the system are: $USERS."


Create a shell script with file name awk1.sh

# using awk:
USERS=`who | awk '{print $1}'`
echo "Users on the system are: $USERS."

In the first example, cut takes its input from the who command. -f1 specifies that the first field is to be cut out from each line, and -d" " specifies that the field delimiter is a space.

In the second example, awk takes its input the same way cut did, then prints the first field (space is the default field delimiter for awk). In general, cut is a much simpler command to use. awk is a full language; scripts can be written using awk as the language instead of the shell script.

3. Using sed editor

Sed is the ultimate stream editor. If that sounds strange, picture a stream flowing through a pipe. Sed has several commands, but most people only learn the substitute command: s. The substitute command changes all occurrences of the regular expression into a new value. A simple example is changing "day" in the "old" file to "night" in the "new" file:

sed s/day/night/ new

Or another way (for Unix beginners),

sed s/day/night/ old >new

and for those who want to test this:

echo day | sed s/day/night/

This will output "night".

Using og quote around argument is recommended. Using the strong (single quote) character, that would be:

sed 's/day/night/' new

The sed editor changes exactly what you tell it to. So if you executed

echo Sunday | sed 's/day/night/' new

This would output the word "Sunnight" bacause sed found the string "day" in the input.

There are four parts to this substitute command:

s -> Substitute command
/../../ -> Delimiter
day -> Regular Expression Pattern Search Pattern
night -> Replacement string

The search pattern is on the left hand side and the replacement string is on the right hand side.

Exercises – Chapter 1

1. Write a sequence of instructions for SIC to ALPHA equal to the product of BETA and GAMMA. Assume that ALPHA, BETA and GAMMA are defined as in Fig.1.3(a).

Assembly Code:

LDA BETA
MUL GAMMA
STA ALPHA
:
:
ALPHA RESW 1
BETA RESW 1
GAMMA RESW 1

2. Write a sequence of instructions for SIC/XE to set ALPHA equal to 4 * BETA – 9. Assume that ALPHA and BETA are defined as in Fig. 1.3(b). Use immediate addressing for the constants.

Assembly Code:

LDA BETA
LDS #4
MULR S,A
SUB #9
STA ALPHA
:
:
ALPHA RESW 1

3. Write SIC instructions to swap the values of ALPHA and BETA.

Assembly Code:

LDA ALPHA
STA GAMMA
LDA BETA
STA ALPHA
LDA GAMMA
STA BETA
:
:
ALPHA RESW 1
BETA RESW 1
GAMMA RESW 1

4. Write a sequence of instructions for SIC to set ALPHA equal to the integer portion of BETA ÷ GAMMA. Assume that ALPHA and BETA are defined as in Fig.1.3(a).

Assembly Code:

LDA BETA
DIV GAMMA
STA ALPHA
:
:
ALPHA RESW 1
BETA RESW 1
GAMMA RESW 1

5. Write a sequence of instructions for SIC/XE to divide BETA by GAMMA, setting ALPHA to the integer portion of the quotient and DELTA to the remainder. Use register-to-register instructions to make the calculation as efficient as possible.

Assembly Code:

LDA BETA
LDS GAMMA
DIVR S, A
STA ALPHA
MULR S, A
LDS BETA
SUBR A, S
STS DELTA
:
:
ALPHA RESW 1
BETA RESW 1
GAMMA RESW 1
DELTA RESW 1

6. Write a sequence of instructions for SIC/XE to divide BETA by GAMMA, setting ALPHA to the value of the quotient, rounded to the nearest integer. Use register-to-register instructions to make the calculation as efficient as possible.

Assembly Code:

LDF BETA
DIVF GAMMA
FIX
STA ALPHA

:
:
ALPHA RESW 1
BETA RESW 1
GAMMA RESW 1

7. Write a sequence of instructions for SIC/XE to clear a 20-byte string to all blanks.

Assembly Code:

LDX ZERO
LOOP LDCH BLANK
STCH STR1,X
TIX TWENTY
JLT LOOP
:
:
STR1 RESW 20
BLANK BYTE C ‘ ‘
ZERO WORD 0
TWENTY WORD 20

8. Write a sequence of instructions for SIC/XE to clear a 20-byte string to all blanks. Use immediate addressing and register-to-register instructions to make the process as efficient as possible.

Assembly Code:

LDT #20
LDX #0
LOOP LDCH #0
STCH STR1,X
TIXR T
JLT LOOP
:
:
STR1 RESW 20

9. Suppose that ALPHA is an array of 100 words, as defined in Fig. 1.5(a). Write a sequence of instructions for SIC to set all 100 elements of the array to 0.

Assembly Code:

LDA ZERO
STA INDEX
LOOP LDX INDEX
LDA ZERO
STA ALPHA, X
LDA INDEX
ADD THREE
STA INDEX
COMP K300
TIX TWENTY
JLT LOOP
:
:
INDEX RESW 1
ALPHA RESW 100
:
ZERO WORD 0
K300 WORD 100
THREE WORD 3

10. Suppose that ALPHA is an array of 100 words, as defined in Fig. 1.5(a). Write a sequence of instructions for SIC/XE to set all 100 elements of the array to 0. Use immediate addressing and register-to-register instructions to make the process as efficient as possible.

Assembly Code:

LDS #3
LDT #300
LDX #0
LOOP LDA #0
STA ALPHA, X
ADDR S, X
COMPR X, T
JLT LOOP
:
:
ALPHA RESW 100

11. Suppose that ALPHA is an array of 100 words. Write a sequence of instruction for SIC/XE to arrange the 100 words in ascending order and store result in an array BETA of 100 elements.

Assembly Code:

NOT YET SOLVED

12. Suppose that ALPHA and BETA are the two arrays of 100 words. Another array of GAMMA elements are obtained by multiplying the corresponding ALPHA element by 4 and adding the corresponding BETA elements.

Assembly Code:

LDS #3
LDT #300
LDX #0
ADDLOOP LDA ALPHA, X
MUL #4
ADD BETA, X
STA GAMMA, X
ADDR S, X
COMPR X, T
JLT ADDLOOP
:
:
ALPHA RESW 100
BETA RESW 100
GAMMA RESW 100

13. Suppose that ALPHA is an array of 100 words. Write a sequence of instructions for SIC/XE to find the maximum element in the array and store results in MAX.

Assembly Code:

LDS #3
LDT #300
LDX #0
CLOOP LDA ALPHA, X
COMP MAX
JLT NOCH
STA MAX
NOCH ADDR S, X
COMPR X, T
JLT CLOOP
:
:
ALPHA RESW 100
MAX WORD -32768

14. Suppose that RECORD contains a 100-byte record, as in Fig. 1.7(a). Write a subroutine for SIC that will write this record on to device 05.

Assembly Code:

JSUB WRREC
:
:
WRREC LDX ZERO
WLOOP TD OUTPUT
JEQ WLOOP
LDCH RECORD, X
WD OUTPUT
TIX LENGTH
JLT WLOOP
RSUB
:
:
ZERO WORD 0
LENGTH WORD 1
OUTPUT BYTE X ‘05’
RECORD RESB 100

15. Suppose that RECORD contains a 100-byte record, as in Fig. 1.7(a). Write a subroutine for SIC that will write this record on to device 05.

Assembly Code:

JSUB WRREC
:
:
WRREC LDX #0
LDT #100
WLOOP TD OUTPUT
JEQ WLOOP
LDCH RECORD, X
WD OUTPUT
TIXR T
JLT WLOOP
RSUB
:
:
OUTPUT BYTE X ‘05’
RECORD RESB 100

16. Write a subroutine for SIC that will read a record into a buffer, as in Fig.1.7(a). The record may be any length from 1 to 100 bytes. The end of record is marked with a “null” character (ASCII code 00). The subroutine should place the length of the record read into a variable named LENGTH.

Assembly Code:

JSUB RDREC
:
:
RDREC LDX ZERO
RLOOP TD INDEV
JEQ RLOOP
RD INDEV
COMP NULL
JEQ EXIT
STCH BUFFER, X
TIX K100
JLT RLOOP
EXIT STX LENGTH
RSUB
:
:
ZERO WORD 0
NULL WORD 0
K100 WORD 1
INDEV BYTE X ‘F1’
LENGTH RESW 1
BUFFER RESB 100

17. Write a subroutine for SIC/XE that will read a record into a buffer, as in Fig.1.7(a). The record may be any length from 1 to 100 bytes. The end of record is marked with a “null” character (ASCII code 00). The subroutine should place the length of the record read into a variable named LENGTH. Use immediate addressing and register-to-register instructions to make the process as efficient as possible.

Assembly Code:

JSUB RDREC
:
:
RDREC LDX #0
LDT #100
LDS #0
RLOOP TD INDEV
JEQ RLOOP
RD INDEV
COMPR A, S
JEQ EXIT
STCH BUFFER, X
TIXR T
JLT RLOOP
EXIR STX LENGTH
RSUB
:
:
INDEV BYTE X ‘F1’
LENGTH RESW 1
BUFFER RESB 100

3. System software Lab Exercises

Refer the blog link

http://studentwebsite.blogspot.com/search/label/System%20Software%20Lap

Additional Shell Programming - Examples

Refer the blog link :

http://studentwebsite.blogspot.com/search/label/Linux%20shell%20programming

Shell Programming - 2nd Exercises

1. Accessing the Variables

a=hello
b="hello world"
maximum=20
echo $a $b $maximum

2. If statement

if date | grep Fri
then
echo Its Friday!
fi

3. Logical Testing

if date | grep Fri && test `date +'%H'` -gt 9
then
echo Its Friday, its hometime!!!
fi

4. If statement and Command Line Arguments

if test "$1" = "Friday"
then
echo "The typed argument is Friday,Welcome to PASS"
fi

5. Case statement

#!/bin/sh
echo \n Command MENU\n
echo a. Current data and time
echo b. Users currently logged in
echo c. Name of the working directory\n
echo Enter a,b, or c: \c
read answer
echo
case $answer in
a)
date
;;
b)
who
;;
c)
pwd
;;
*)
echo There is no selection: $answer
;;
esac

6. For Loop

for i in 3 7
do
echo " $i * 5 is `expr $i \* 5` "
done

7. File name printing using for loop

#!/bin/bash
for filename in *
do
echo $filename
done

8. While loop

read i
while test "$i" -gt 0
do
i=`expr $i - 1`
echo $i
done

9. While with Input string

INPUT_STRING=hello
while [ "$INPUT_STRING" != "bye" ]
do
echo "Please type something in (bye to quit)"
read INPUT_STRING
echo "You typed: $INPUT_STRING"
done

10. Function

hello()
{
k1=`expr $1 \* $2`
echo $k1
return
}
echo The example of function.
hello $1 $2