Shell functions intialisation. Put this script in /etc/profile.d/

function.sh

setproxy()
{
    proxyhostport="my.proxy.com:portnbr"
    authok=0
    while [ $authok -eq 0 ] ; do
        echo "Setting proxy environment variables:"
        echo -n "  Username: "
        read -e username
        echo -n "  Password: "
        read -es password
        ret=$(curl -s -D - -x http://${username}:${password}@${proxyhostport} \
                   -o /dev/null http://www.example.org | head -n 1 | tr -d '\n\r')
        echo
        if [ "$ret" == "HTTP/1.0 200 OK" ] ; then
            authok=1
        else
            echo "  *** ERROR: authentification failed ('$ret') ***"
        fi
    done
    export http_proxy="http://${username}:${password}@${proxyhostport}"
    export https_proxy=$http_proxy
    export ftp_proxy=$http_proxy
    export no_proxy="$(hostname),*.my.domain.com,localhost,127.0.0.0/8,10.0.0.0/8,172.16.0.0/12,192.168.0.0/16"
    echo "Proxy environment variables set"
}