Question

Design two shell programs working on Linux (Ubuntu)

1. Design a shell script program, 1) reading given only two integer numbers from command line arguments and computing their multiplication. If two integer numbers are not given, print “Wrong Input” on your screen. Note that, the number of arguments is known when the script runs.

Take a screenshot showing your shell program and its execution step.

2. Design a shell program to remove all the shell programming files ending with sh on your home directory when a SIGINT signal is received.

Take three screenshots (The first screenshot shows one or more sh files on your home directory, and the second screenshot shows your shell program and its execution step, the third screenshot shows that sh files do not exist in your home directory after executing your shell program).

Submit your four screenshots.

Answer 1

First program

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

#! /bin/sh

required=2

if [ $# -eq $required ]

then

result = `expr $1 \* $2`

echo "$result"

else

echo "Wrong Input"

fi

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

In this program ,number of command line agruments is given by $# and is compared by required

then to calculate an expression expr is used as in script above  

Screenshot

Program 2

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

#! /bin/sh

directory = "/home/viju4076" #home directory of user

echo "The PID is $$" #required for killing the process

sigint()

{

echo "SIGINT signal received"

for filename_full in "$directory"/*

do

filename= $(basename -- "$filename_full")

extension="${filename##*.}"

if [ "$extension" = "sh" ]

then

rm "$filename_full"

fi

done

exit 0

}

trap 'sigint' INT

while true ; do

sleep 30

done

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

In this program first we store the required path in directory variable ..Then display the PID so that signal could be send to this process by another terminal or one could use ctrl+C which also gives the same signal to the process.

Then the required work is written in sigint() function ..which gets call when signal SIGINT is received..then in function ..traverse each file get the extension and if it matches with sh then remove the file by rm command...

at last run a loop infinte times so that SIGINT can be received before ending of the script..

Screenshots