You are missing several quotes and your spaces inside your square brackets are off. Just do it like this:

#!/bin/bash



if ping -c 1 InternalIpOfEquipment; then

    /usr/bin/curl -x ProxyIP:443 --output /tmp/vlc.dmg "$fileURL"

else

    /usr/bin/curl --output /tmp/vlc.dmg "$fileURL"

fi



exit 0

You can also do it like this where you have three checks:
1. Verify that the client IP address is 10.X.X.X
2. Verify that a dns lookup to a specific domain returns an ip of 10.X.X.X (rather than an external IP)
3. Verify that you can ping a specific internal server successfully

#!/bin/bash



function internal_network_test () {

    local domain="contoso.com"

    local internalServer="internalserver.contoso.com"



    echo "Performing internal network tests..."

    # Test that a user's IP address is an internal IP address

    addresses=$(ifconfig -a inet 2>/dev/null | sed -n -e '/127.0.0.1/d' -e '/0.0.0.0/d' -e '/inet/p' | awk '{print $2}')

    for address in $addresses; do

        if [[ "$address" =~ (^127.)|(^172.1[6-9].)|(^172.2[0-9].)|(^172.3[0-1].)|(^192.168.) ]]; then

            echo "Internal network test (Device IP) failed."

            return 1

        fi

    done



    # Test that DNS lookups find internal addresses, not external

    addresses=$(nslookup "$domain" | grep -A 1 "Name:" | grep "Address:" | awk '{print $2}')

    for address in $addresses; do

        if [[ ! "$address" =~ (^10.) ]]; then

            echo "Internal network test (DNS Lookup) failed."

            return 1

        fi

    done



    # Test for internal connectivity via Ping

    if ! ping -c 2 -o "$internalServer" &> /dev/null; then

        echo "Internal network test (Ping) failed."

        return 1

    fi

}



if internal_network_test; then

    echo "Device is internal."

   /usr/bin/curl -x ProxyIP:443 --output /tmp/vlc.dmg "$fileURL"

else

    echo "Device is external."

    /usr/bin/curl --output /tmp/vlc.dmg "$fileURL"

fi



exit 0

thanks a lot.
it works perfectly and now a know how to :)