amming The .sh script can be run with either 0, 2, 3, or 5 command-line arguments. As a basic sanity check, Your program should test at the beginning that the number of arguments given is one of these. If not, the user has entered something incorrectly, and the script should output the error message Usage: ./portscanner.sh [-t timeout] [host startport stopport], and immediately exit.
Penetration
The .sh script can be run with either 0, 2, 3, or 5 command-line arguments. As a basic sanity check, Your program should test at the beginning that the number of arguments given is one of these. If not, the user has entered something incorrectly, and the script should output the error message
Usage: ./portscanner.sh [-t timeout] [host startport stopport],
and immediately exit.
.sh
#!/bin/bash
# Basic bash port scanner
# CHECKING CONDITION FOR -t OPTION
if [ "$1" == '-t' ]; then
# IF -t IS USED
time=$2
host=$3
startport=$4
stopport=$5
else
# IF -t IS NOT USED
time=2
host=$1
startport=$2
stopport=$3
fi
function pingcheck
{
pingresult=$(ping -c 1 $host | grep bytes | wc -l)
if [ "$pingresult" -gt 1 ]; then
echo
else
echo "$host is down, quitting"
exit
fi
}
function portcheck
{
# IF TIMEOUT VALUE OF LESS THAN 1
if [ "$time" -lt 1 ]
then
echo "Timeout value must be greater than 0, quitting"
exit
# IF TIMEOUT VALUE IF NOT EQUAL TO 2
elif [ "$time" -ne 2 ]
then
echo "Note: Timeout changed to $time."
fi
for ((counter=$startport; counter<=$stopport; counter++))
do
if timeout $time bash -c "echo >/dev/tcp/$host/$counter"
then
echo "$counter open"
else
echo "$counter closed"
fi
done
}
#first, check that the host is alive
pingcheck
# next, loop through the ports
portcheck
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