Bash Script - syntax error: operand expected [closed]-CodePudding

I'm trying to make a simple port scanner bash script and I keep running into this error.

./tcpscan.sh: line 10: ((: counter=: syntax error: operand expected (error token is "=")

tcpscan.sh

#!/usr/bin/bash

host=$1
firstport=$2
lastport=$3

function portscan
{
for ((counter=$fristport; counter<=$lastport; counter  ))
do
        (echo >/dev/tcp/$host/$counter) > /dev/null 2>&1 && echo "$counter open"
done
}

portscan

CodePudding user response：

The error is caused because you are trying to set the value of counter to a non-existent value. Fix the transposed characters in your variable name.

CodePudding user response：

#!/usr/bin/bash

host=$1
firstport=$2
lastport=1$3


function portscan
{


for ((i = ${firstport} ; i <= ${lastport} ; i  ))
do
 echo "/dev/tcp/$host/$i" >> /dev/null 2>&1 && echo "$i open"
done


}

portscan