ip-address操作

Question

I have some ip-addresses that a user gives:

192.168.50.$i

now I want to do +200 with $i . So if the user does:

bash script 52 20 56

The result must be

ping 192.168.50.252 , ...

I thought to do something like:

function
{
  $i = $i + 200
  ping 192.168.50.$i
}

And what can I do when it's higher then 255?

Answer 1

You can do something like this...

echo "192.168.50.$(( $i + 200 ))"

If you wanted to check if it is greater than 255 you will have to break it down a bit.

fourth=$(( $i + 200 ))
if (( fourth > 255 ))
then
    echo "Greater than 255!"
    exit 1
fi

Question change Didn't see last part

You could create a function but this wont work as the syntax is way out.

function
{
    $i = $i + 200
    ping 192.168.50.$i
}

You will need to do something like this...

# Function name
function ip_assess {

    # $1 takes the first input to the function
    # There is no $ when assigning to a variable
    # There is no spaces around the = when assigning
    i=$(( $1 + 200 ))

    # No need for $ when doing arithmetic comparisons
    if (( i > 255 ))
    then
        # Return an error code of 1 from this function
        return 1
    fi

    # -c 4 will get it to ping four times and return and not continuously
    # If the ping is a success return 0 (a pass). If no then 2 (different error code)
    ping "192.168.50.$i" -c 4 && return 0 || return 2

}

ip_assess 30
# Grab the error code
valid_ip=$?

case $valid_ip in
    0 )
        echo "Valid IP"
    ;;
    1 )
        echo "IP is to high"
    ;;
    2 )
        echo "IP not alive"
    ;;
esac