Database System Concepts
Database System Concepts
7th Edition
ISBN: 9780078022159
Author: Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Publisher: McGraw-Hill Education
Bartleby Related Questions Icon

Related questions

bartleby

Concept explainers

Question

penetration programming

Modify your .sh program to accept an optional command-line argument -t, followed by a space and an additional numerical argument, which sets the timeout value for the echo command in the portcheck function. The argument must come before the hostname and start and stop ports. If the argument is not given, the timeout should remain at a default value of 2. If the argument is given, in addition to changing the timeout, the script should print out an informational message “Timeout changed to <value>”.

For example, ./portscanner.sh -t 3 www.yahoo.com 40 80 should change the default timeout for each write to /dev/tcp to 3 seconds.

Note: adding this feature will also require you to change the way you scan and save the command line arguments for hostnames. The number and place of command line arguments will now vary depending on whether the user uses the ’-t’ option or not. You will have to add program logic to account for this, so that everything works correctly in either case.

.sh program

#!/bin/bash
# bash port scanner

# get the host to scan from the command line
host=$1
startport=$2
stopport=$3


function pingcheck
{

# run a ping command and scrape its output to see if it succeeded
pingresult=$(ping -c 1 $host | grep bytes | wc -l)
if [ "$pingresult" -gt 1 ]
then
    echo "$host is up"
else
    echo "$host is down, quitting"
    exit
fi
}

function portcheck
{

for ((counter=$startport; counter <= $stopport; counter++))
do
    if timeout 2 bash -c "echo > /dev/tcp/$host/$counter"
    then 
        echo "$counter is open"
    else
        echo "$counter is closed"
    fi
done
}

pingcheck

portcheck

Expert Solution
Check Mark
Knowledge Booster
Background pattern image
Computer Science
Learn more about
Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, computer-science and related others by exploring similar questions and additional content below.
Similar questions
SEE MORE QUESTIONS
Recommended textbooks for you
Text book image
Database System Concepts
Computer Science
ISBN:9780078022159
Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Publisher:McGraw-Hill Education
Text book image
Starting Out with Python (4th Edition)
Computer Science
ISBN:9780134444321
Author:Tony Gaddis
Publisher:PEARSON
Text book image
Digital Fundamentals (11th Edition)
Computer Science
ISBN:9780132737968
Author:Thomas L. Floyd
Publisher:PEARSON
Text book image
C How to Program (8th Edition)
Computer Science
ISBN:9780133976892
Author:Paul J. Deitel, Harvey Deitel
Publisher:PEARSON
Text book image
Database Systems: Design, Implementation, & Manag...
Computer Science
ISBN:9781337627900
Author:Carlos Coronel, Steven Morris
Publisher:Cengage Learning
Text book image
Programmable Logic Controllers
Computer Science
ISBN:9780073373843
Author:Frank D. Petruzella
Publisher:McGraw-Hill Education